Rare earth enrichment process by contacting raw material with a base at specific pH values

ABSTRACT

Disclosed herein are methods for preparing a hydraulic pre-concentrate enriched in rare earth elements and critical minerals, the method comprising: (a) contacting a raw material with a first base in an amount sufficient to adjust the pH to a value from about 4.0 to about 6.0, thereby forming a mixture comprising a first aqueous phase and a first solid concentrate; (b) separating the first aqueous phase from the first solid concentrate; (c) contacting the first aqueous phase with a second base in an amount sufficient to adjust the pH to a value from about 7.0 to about 9.0, thereby forming a mixture comprising a second aqueous phase and the hydraulic pre-concentrate; (d) removing the second aqueous phase and collecting the hydraulic pre-concentrate; wherein the raw material comprises rare earth elements; and wherein the hydraulic pre-concentrate is enriched in rare earth elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/706,584, filed on Mar. 28, 2022, which is a continuation-in-part ofco-pending U.S. application Ser. No. 17/115,128, filed on Dec. 8, 2020,which is a continuation of and claims the benefit of U.S. applicationSer. No. 16/795,471, filed on Feb. 19, 2020, which claims the benefit ofU.S. Provisional Application No. 62/875,502, filed on Jul. 17, 2019,each of which is incorporated herein by reference in its entirety; andthis application is also a continuation-in-part of co-pending U.S.application Ser. No. 17/627,484, filed on Jan. 14, 2022, a nationalstage application of International Application Serial No.PCT/US2020/042674, filed on Jul. 17, 2020, which claims the benefit ofU.S. Provisional Application No. 62/875,502, filed on Jul. 17, 2019, andU.S. Utility application Ser. No. 16/795,471, filed Feb. 19, 2020, eachof which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with U.S. Government support under grant numberDE-FE0031524 awarded by the U.S. Department of Energy. The U.S.government has certain rights in the invention.

BACKGROUND

Rare earth elements (REEs) are useful and necessary for the manufactureof batteries that power hybrid and electric vehicles, catalyticconverters, computer memory, fluorescent lighting and lasers,smartphones and tablet computers, cameras including electroniccomponents and lenses, e-readers, magnets, night-vision goggles, GPS andcommunications equipment, military applications includingprecision-guided weapons and vehicle armor, aircraft engines, personalprotective equipment, and in other applications including defenseapplications. Some REEs can be used in air pollution control mechanisms,oil refineries, in medical diagnostic equipment such as, for example,X-ray and MRI machines, as phosphors, as catalysts, as components ofceramics and paints, and/or as polishing compounds. Although REEs andcritical minerals (CM) can be extracted from many waste products andores, few such resources are economically attractive. Due to current andpossibly continuing export controls for REEs from China, it would bedesirable to develop domestic sources of REEs.

Acid mine drainage (AMD) is a pollutant generated by coal and othermines and must be treated in compliance with federal and state cleanwater regulations to adjust pH and remove metal ions including iron,aluminum, and manganese. There are vast instances of acid mine drainage(AMD) in the northern, central, and southern Appalachian basins, as wellas the Illinois coal basin and elsewhere in the U.S. Across the northernand central Appalachian Coal Basins, water pollution caused by AMD isthe single greatest cause of stream impairment. Processes for treatingAMD for regulatory compliance have been the subject of massive researchand infrastructure investments since the early 1970s. It is estimatedthat, in the Appalachian states alone, more than 50 new, large AMDtreatment plants will be installed in the next 10 years, in an effort toaddress increasing stream pollution. Although trace amounts of REEs areknown to exist in AMD, a reliable method of concentrating and extractingthem has not yet been developed.

Despite advances in the treatment of acid mine drainage, there is stilla scarcity of methods that are able to recover REEs from AMD and thatare environmentally sound, inexpensive, scalable, and able to beretrofitted to existing plants. Ideally, the method would produceinsignificant amounts of naturally-occurring radioactive material and/orother noxious wastes as well as reducing stream pollution. Additionally,it would be desirable if the method could be adapted to extract REEsfrom other sources. It would also be advantageous for the process tooperate continuously and without forming insoluble material such as, forexample, aluminosilicate gels. It would further be desirable to have adomestic source of REEs. These needs and other needs are satisfied bythe present disclosure.

SUMMARY

In accordance with the purpose(s) of the present disclosure, as embodiedand broadly described herein, the disclosure, in one aspect, relates toa process for treating acid mine drainage to comply with Clean Water Actrequirements while simultaneously recovering a high-grade rare earthconcentrate suitable for extraction of commercially valuable rare earthoxides. In a further aspect, the high-grade rare earth preconcentrate isfrom about 0.1% to about 5% total rare earth elements (“REEs”) on a dryweight basis. The disclosed processes may be a continuous processcomprising discrete modules or steps as disclosed herein such that thediscrete modules or steps are co-located at or near a site or source ofacid mine discharge. In other aspects, the disclosed processes can beseparated geographically and at different sites, e.g., one processmodule or site comprising disclosed methods may co-located at a site orsource of acid mine discharge and produces a hydraulic pre-concentratecomposition that is transported to a second module or site. The secondmodule or site may comprise disclosed methods for utilizing thehydraulic pre-concentrate as a source material for production of apregnant leach solution composition. The pregnant leach solutioncomposition may then be transported to a third module or site comprisingdisclosed methods for utilizing the pregnant leach composition forproduction of one or more rare earth element oxides using solventexchange methods. The one or more rare earth elements may be utilized atthe third site for further processing to one or more reduced rare earthmetal or a rare earth metal powder using disclosed methods.Alternatively, the one or more rare earth element oxides produced at thethird module or site may be transported to a fourth module or site forfurther processing to one or more reduced rare earth metal or a rareearth metal powder using disclosed methods. Also disclosed herein is amethod for processing the rare earth preconcentrate to generate a PLSthat does not form gels or emulsions and that is suitable for processingvia solvent extraction. In another aspect, disclosed herein is a systemthat includes a plant capable of carrying out the method disclosedherein. In yet another aspect, disclosed herein is a compositioncontaining the REEs prepared by the disclosed process.

Disclosed herein are methods for preparing a hydraulic pre-concentrateenriched in rare earth elements and critical minerals, the methodcomprising: (a) contacting a raw material with a first base in an amountsufficient to adjust the pH to a value from about 4.0 to about 6.0,thereby forming a mixture comprising a first aqueous phase and a firstsolid concentrate; (b) separating the first aqueous phase from the firstsolid concentrate; (c) contacting the first aqueous phase with a secondbase in an amount sufficient to adjust the pH to a value from about 7.0to about 9.0, thereby forming a mixture comprising a second aqueousphase and the hydraulic pre-concentrate; (d) removing the second aqueousphase and collecting the hydraulic pre-concentrate; wherein the rawmaterial comprises rare earth elements; and wherein the hydraulicpre-concentrate is enriched in rare earth elements.

Also disclosed herein are methods for preparing a pregnant leachsolution, the method comprising: transferring a disclosed firstconditioned hydraulic pre-concentrate or a disclosed second conditionedhydraulic pre-concentrate to a mixing tank; and adding a first acid tothe mixing tank in an amount sufficient to adjust the pH from about 2.0to about 4.0, thereby forming the pregnant leach solution; wherein thefirst acid is mixed with the first conditioned hydraulic pre-concentrateor the second conditioned hydraulic pre-concentrate as the first acid isadded.

Also disclosed herein are methods for preparing a pregnant leachsolution, the method comprising: transferring a hydraulicpre-concentrate to a mixing tank; and adding a first acid to the mixingtank in an amount sufficient to adjust the pH from about 2.0 to about4.0, thereby forming the pregnant leach solution; wherein the hydraulicpre-concentrate is enriched in rare earth elements compared to the rareearth elements concentration present in an acid mine discharge; andwherein the first acid is mixed with the hydraulic pre-concentrate asthe first acid is added.

Also disclosed herein are methods for making a rare earth element oxide,the method comprising the steps of: providing a rare earth element oxidefeedstock material; subjecting the rare earth element oxide feedstockmaterial to one or more solvent extraction steps; and isolating the rareearth element oxide from the one or more solvent extraction steps;wherein the rare earth element oxide feedstock material comprises adisclosed hydraulic pre-concentrate, a disclosed pregnant leachsolution, or combination thereof.

Also disclosed herein are methods for making a rare earth element oxide,the method comprising the steps of: providing a rare earth element oxidefeedstock material; subjecting the rare earth element oxide feedstockmaterial to one or more solvent extraction steps; and isolating the rareearth element oxide from the one or more solvent extraction steps;wherein the rare earth element oxide feedstock material comprises ahydraulic pre-concentrate, a pregnant leach solution, or combinationthereof.

Also disclosed are hydraulic pre-concentrate compositions.

Also disclosed are hydraulic pre-concentrate compositions prepared bythe disclosed methods.

Also disclosed are pregnant leach solution compositions.

Also disclosed are pregnant leach solution compositions prepared by thedisclosed methods.

Also disclosed are rare earth element oxides.

Also disclosed are rare earth element oxides prepared by the disclosedmethods.

Also disclosed are reduced rare earth element compositions or rare earthelement powders.

Also disclosed are reduced rare earth element compositions or rare earthelement powders prepared by the disclosed methods.

Other systems, methods, features, and advantages of the presentdisclosure will be or become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features, andadvantages be included within this description, be within the scope ofthe present disclosure, and be protected by the accompanying claims. Inaddition, all optional and preferred features and modifications of thedescribed embodiments are usable in all aspects of the disclosure taughtherein. Furthermore, the individual features of the dependent claims, aswell as all optional and preferred features and modifications of thedescribed embodiments are combinable and interchangeable with oneanother.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIGS. 1A-1B show a representative mobile Rare Earth Element/CriticalMineral (REE/CM) extraction unit at an Acid Mine Drainage (AMD)treatment plant useful in one aspect of the disclosure herein. FIG. 1A:trailer containing extraction unit. FIG. 1B: interior of trailer showingplate and frame filters (foreground) and mixing tanks (background).

FIGS. 2A-2B show representative analysis of samples treated by thedisclosed process. FIG. 2A: example composition of Acid Mine Drainage(AMD) preconcentrate and oxide composition after processing through anAcid Leaching/Solvent Extraction (ALSX) process as disclosed herein. Notshown are elements making up less than 0.01% of the sample (i.e., Co,Mg, Mn, Ni). FIG. 2B: elemental distribution within the Mixed Rare EarthOxide (MREO) fraction. Boxed element labels indicate critical minerals.Light Rare Earth Elements (LREE) (35.3%) are indicated by inset text,“LREE”, adjacent to the element label, and HREE (64.7%) represent thebalance. Sample was not acid washed prior to analysis.

FIG. 3 shows a schematic flow diagram of a process disclosed herein.Conventional AMD treatment appears on the left (darker gray background)with Rare Earth Element/Critical Mineral (REE/CM) recovery andconcentration on the right (light gray background).

FIGS. 4A-4B each show exemplary aspects of a Rare Earth ExtractionFacility (REEF).

FIG. 5 shows Acid Leaching/Solvent Extraction (ALSX) units before (left)and after (right) development and implementation of measures developedto control crud formation.

FIG. 6 is a flow diagram showing individual stages according to oneaspect of the integrated upstream concentration and AcidLeaching/Solvent Extraction (ALSX) process as disclosed herein.

FIGS. 7A-7B show representative sensitivity analyses of disclosedprocesses. FIG. 7A shows representative sensitivity analysis of maximumacid dose as a function of sludge feed grade. FIG. 7B showsrepresentative sensitivity analysis of breakeven shipping distance as afunction of feed grade and moisture.

FIG. 8 shows sensitivity analyses of Acid Leaching/Solvent Extraction(ALSX) operating cost as a function of plant size and feed grade.

FIG. 9 shows a photographic image of representative high grade (80%)rare earth concentrate produced by a process disclosed herein.

FIG. 10 is a flow diagram of an operating principle of a representativemobile plant as disclosed herein for implementing the disclosed methodsand processes. The Omega Clarifier as labeled in the figure is anelement of a specific conventional Acid Mine Drainage (AMD) treatmentplant in West Virginia.

FIG. 11 shows an exemplary acid leaching module of a bench-scale plantas disclosed herein.

FIG. 12 shows representative Pregnant Leach Solution (PLS) gel formationon a pan filter at pH 3.0. In one aspect, the method disclosed hereindoes not exhibit gel formation.

FIGS. 13A-13B show representative components useful in the processesdisclosed herein. FIG. 13A shows a 150 mm lab scale filter press; andFIG. 13B shows a 420 mm filter press.

FIGS. 14A-14B show photographic images of aspects of filtration ofPregnant Leach Solution (PLS). FIG. 14A shows a representative PregnantLeach Solution (PLS) solution after filtration in plate and framefilters; and FIG. 14B shows a representative filter cake from cleaning a2 ft³ filter press used to process the Pregnant Leach Solution (PLS).

FIG. 15 is a flow diagram showing the acid leaching process used togenerate the Pregnant Leach Solution (PLS) as disclosed herein.

FIG. 16 shows an exemplary Solvent Extraction (SX) module useful in theprocesses disclosed herein.

FIG. 17 shows crud formation in an extraction settler during DLM (a siteused as a source of Acid Mine Drainage (AMD) treatment solids) shakedowntesting.

FIG. 18 is a representative flow diagram for a solvent extraction moduledisclosed herein.

FIG. 19 shows an exemplary precipitation module useful in the processesdisclosed herein that can be used to recover Rare Earth Elements (REEs)from stripped raffinate.

FIG. 20 shows is a diagram of a representative precipitation processuseful in the methods and processes disclosed herein.

FIG. 21 shows a photographic image of a representative Mixed Rare EarthOxide (MREO) product with 62% grade produced by an example process asdisclosed herein.

FIG. 22 shows representative data for distribution of Acid Mine Drainage(AMD) Rare Earth Elements (REE) concentrations as a function of pH,where Central Appalachian coal basin AMD source (CAPP) and NorthernAppalachian coal basin AMD source (NAPP) represent, respectively,sources enriched in Rare Earth Elements (REEs).

FIG. 23 shows a flow chart of a portion of a disclosed process, startingwith transfer of raw Acid Mine Drainage (AMD) feedstock to a separatorand ending with transfer of a Pregnant Leach Solution (PLS) to thedisclosed solvent extraction process. An optional series of steps forrecovering scandium are included.

FIG. 24 shows a flow diagram of a disclosed process. In various aspects,a second separation and concentration step can be applied if it isdesired to collect a scandium-enriched solid concentrate.

FIGS. 25A-25B show a flow chart of a disclosed process for preparationof a hydraulic preconcentrate Hydraulic Pre-Concentrate (HPC) andPregnant Leach Solution (PLS). FIG. 25A shows steps 700-729 of adisclosed process for preparation of a Hydraulic Pre-Concentrate (HPC)and Pregnant Leach Solution (PLS). FIG. 25B a disclosed process forpreparation of a Hydraulic Pre-Concentrate (HPC) and Pregnant LeachSolution (PLS) continuing step 729 in FIG. 25A to steps 750-742 of FIG.25B.

FIGS. 26A-26B show representative disclosed processes for processing ofAcid Mine Drainage (AMD) through various subprocesses to preparation ofa Pregnant Leach Solution (PLS) and storage of same. FIG. 26A shows arepresentative disclosed process for processing of Acid Mine Drainage(AMD) through various subprocesses to preparation of a Pregnant LeachSolution (PLS) and storage of same in which primary and secondary conetanks are utilized after clarifier #2 to dewater the hydraulicpreconcentrate. FIG. 26B shows a representative disclosed process forprocessing of Acid Mine Drainage (AMD) through various subprocesses topreparation of a Pregnant Leach Solution (PLS) and storage of same inwhich geobags are utilized after clarifier #2 to dewater the hydraulicpreconcentrate.

FIGS. 27A-27B show the show representative disclosed processes forprocessing of Acid Mine Drainage (AMD through various subprocesses topreparation of a Pregnant Leach Solution (PLS) and storage of same fromFIGS. 26A-26B that have been segregated into subprocesses as shownherein FIGS. 27A-27B. FIG. 27A shows a representative disclosed processfor processing of Acid Mine Drainage (AMD) through various subprocessesto preparation of a Pregnant Leach Solution (PLS) and storage of same inwhich primary and secondary cone tanks are utilized after clarifier #2to dewater the hydraulic preconcentrate in which the process of shown inFIG. 26A is subdivided into four subprocesses which may occur on fourdiscrete sites labeled as Sites #1-4. FIG. 26B shows a representativedisclosed process for processing of Acid Mine Drainage (AMD) throughvarious subprocesses to preparation of a Pregnant Leach Solution (PLS)and storage of same in which geobags are utilized after clarifier #2 todewater the hydraulic preconcentrate in which the process shown FIG. 26Bis subdivided into four subprocesses which may occur on four discretesites labeled as Sites #1-4.

Additional advantages of the invention will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or can be learned by practice of the invention. Theadvantages of the invention will be realized and attained by means ofthe elements and combinations particularly pointed out in the appendedclaims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive of the invention, as claimed.

DETAILED DESCRIPTION

Many modifications and other embodiments disclosed herein will come tomind to one skilled in the art to which the disclosed compositions andmethods pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the disclosures are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims. Theskilled artisan will recognize many variants and adaptations of theaspects described herein. These variants and adaptations are intended tobe included in the teachings of this disclosure and to be encompassed bythe claims herein.

Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentdisclosure.

Any recited method can be carried out in the order of events recited orin any other order that is logically possible. That is, unless otherwiseexpressly stated, it is in no way intended that any method or aspect setforth herein be construed as requiring that its steps be performed in aspecific order. Accordingly, where a method claim does not specificallystate in the claims or descriptions that the steps are to be limited toa specific order, it is no way intended that an order be inferred, inany respect. This holds for any possible non-express basis forinterpretation, including matters of logic with respect to arrangementof steps or operational flow, plain meaning derived from grammaticalorganization or punctuation, or the number or type of aspects describedin the specification.

All publications mentioned herein are incorporated herein by referenceto disclose and describe the methods and/or materials in connection withwhich the publications are cited. The publications discussed herein areprovided solely for their disclosure prior to the filing date of thepresent application. Nothing herein is to be construed as an admissionthat the present invention is not entitled to antedate such publicationby virtue of prior invention. Further, the dates of publication providedherein can be different from the actual publication dates, which canrequire independent confirmation.

While aspects of the present disclosure can be described and claimed ina particular statutory class, such as the system statutory class, thisis for convenience only and one of skill in the art will understand thateach aspect of the present disclosure can be described and claimed inany statutory class.

It is also to be understood that the terminology used herein is for thepurpose of describing particular aspects only and is not intended to belimiting. Unless defined otherwise, all technical and scientific termsused herein have the same meaning as commonly understood by one ofordinary skill in the art to which the disclosed compositions andmethods belong. It will be further understood that terms, such as thosedefined in commonly used dictionaries, should be interpreted as having ameaning that is consistent with their meaning in the context of thespecification and relevant art and should not be interpreted in anidealized or overly formal sense unless expressly defined herein.

Prior to describing the various aspects of the present disclosure, thefollowing definitions are provided and should be used unless otherwiseindicated. Additional terms may be defined elsewhere in the presentdisclosure.

Definitions.

As used herein, “comprising” is to be interpreted as specifying thepresence of the stated features, integers, steps, or components asreferred to, but does not preclude the presence or addition of one ormore features, integers, steps, or components, or groups thereof.Moreover, each of the terms “by”, “comprising,” “comprises”, “comprisedof,” “including,” “includes,” “included,” “involving,” “involves,”“involved,” and “such as” are used in their open, non-limiting sense andmay be used interchangeably. Further, the term “comprising” is intendedto include examples and aspects encompassed by the terms “consistingessentially of” and “consisting of.” Similarly, the term “consistingessentially of” is intended to include examples encompassed by the term“consisting of.

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a rare earthelement” includes, but is not limited to, mixtures of two or more suchrare earth elements, and the like.

It should be noted that ratios, concentrations, amounts, and othernumerical data can be expressed herein in a range format. It will befurther understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint. It is also understood that there are a number ofvalues disclosed herein, and that each value is also herein disclosed as“about” that particular value in addition to the value itself. Forexample, if the value “10” is disclosed, then “about 10” is alsodisclosed. Ranges can be expressed herein as from “about” one particularvalue, and/or to “about” another particular value. Similarly, whenvalues are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms a furtheraspect. For example, if the value “about 10” is disclosed, then “10” isalso disclosed.

When a range is expressed, a further aspect includes from the oneparticular value and/or to the other particular value. For example,where the stated range includes one or both of the limits, rangesexcluding either or both of those included limits are also included inthe disclosure, e.g. the phrase “x to y” includes the range from ‘x’ to‘y’ as well as the range greater than ‘x’ and less than ‘y’. The rangecan also be expressed as an upper limit, e.g. ‘about x, y, z, or less’and should be interpreted to include the specific ranges of ‘about x’,‘about y’, and ‘about z’ as well as the ranges of ‘less than x’, lessthan y′, and ‘less than z’. Likewise, the phrase ‘about x, y, z, orgreater’ should be interpreted to include the specific ranges of ‘aboutx’, ‘about y’, and ‘about z’ as well as the ranges of ‘greater than x’,greater than y′, and ‘greater than z’. In addition, the phrase “about‘x’ to ‘y’”, where ‘x’ and ‘y’ are numerical values, includes “about ‘x’to about ‘y’”.

It is to be understood that such a range format is used for convenienceand brevity, and thus, should be interpreted in a flexible manner toinclude not only the numerical values explicitly recited as the limitsof the range, but also to include all the individual numerical values orsub-ranges encompassed within that range as if each numerical value andsub-range is explicitly recited. To illustrate, a numerical range of“about 0.1% to 5%” should be interpreted to include not only theexplicitly recited values of about 0.1% to about 5%, but also includeindividual values (e.g., about 1%, about 2%, about 3%, and about 4%) andthe sub-ranges (e.g., about 0.5% to about 1.1%; about 5% to about 2.4%;about 0.5% to about 3.2%, and about 0.5% to about 4.4%, and otherpossible sub-ranges) within the indicated range.

As used herein, the terms “about,” “approximate,” “at or about,” and“substantially” mean that the amount or value in question can be theexact value or a value that provides equivalent results or effects asrecited in the claims or taught herein. That is, it is understood thatamounts, sizes, formulations, parameters, and other quantities andcharacteristics are not and need not be exact, but may be approximateand/or larger or smaller, as desired, reflecting tolerances, conversionfactors, rounding off, measurement error and the like, and other factorsknown to those of skill in the art such that equivalent results oreffects are obtained. In some circumstances, the value that providesequivalent results or effects cannot be reasonably determined. In suchcases, it is generally understood, as used herein, that “about” and “ator about” mean the nominal value indicated ±10% variation unlessotherwise indicated or inferred. In general, an amount, size,formulation, parameter or other quantity or characteristic is “about,”“approximate,” or “at or about” whether or not expressly stated to besuch. It is understood that where “about,” “approximate,” or “at orabout” is used before a quantitative value, the parameter also includesthe specific quantitative value itself, unless specifically statedotherwise.

As used herein, the term “effective amount” refers to an amount that issufficient to achieve the desired modification of a physical property ofthe composition or material. For example, an “effective amount” of abuffer refers to an amount that is sufficient to achieve the desiredimprovement in the property modulated by the formulation component, e.g.achieving and maintaining a desired solution pH. The specific level interms of wt % in a composition required as an effective amount willdepend upon a variety of factors including the amount and type ofbuffer, size of processing plant (i.e., bench top, mobile, or commercialscale), amount and type of feedstock being treated, and end use of theREEs recovered during the process.

As used herein, the terms “optional” or “optionally” means that thesubsequently described event or circumstance can or cannot occur, andthat the description includes instances where said event or circumstanceoccurs and instances where it does not.

As used herein, the term “rare earth element” (REE) is refers to acomposition comprising one or more rare earth elements, including one ormore of a lanthanide chemical element, i.e., lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium. andcan sometimes also include the elements scandium and yttrium. Theelements scandium and yttrium often occur in the same ore deposits aslanthanides and also have some similar chemical properties. Rare earthelements are useful in a variety of applications in the electronics,defense, and medical industries, as well as in other applications. Anoxide of a rare earth element is a “rare earth oxide” and can be usedfor analytical purposes or may be useful as a component of ceramics,catalysts, and/or coatings, among other uses. It is to be understoodthat when referencing rare earth elements that any of the elements canbe present in a zero valence or elemental state, or in an ionized orvalence state associated in the art with the individual element, and allforms are understood to be collectively included within the meaning of“rare earth elements”. Moreover, it is to be understood that referenceto any individual rare earth element, i.e., any one of lanthanum,cerium, praseodymium, neodymium, promethium, samarium, europium,gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium,lutetium, including scandium and yttrium, can be present in a zerovalence or elemental state, or in an ionized or valence state associatedin the art with the given element, and all forms are understood to becollectively included within the meaning of reference to said element.For example, reference to “lanthanum”, “an element such as lanthanum”,“a composition comprising lanthanum”, and the like, it is understoodthat the reference inclusive any or all forms of lanthanum such as La⁰,La⁺¹, La⁺², and La⁺³. It is further understood that a reference to anygiven rare earth element is inclusive of all isotopic forms of theelement.

As used herein, the terms “heavy rare earth elements” and “HREE” can beused interchangeably and refer to yttrium, gadolinium, terbium,dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. It is tobe understood that yttrium can be classified as a heavy rare earthelement due to chemical properties and co-location with other HREEs inores, but can also be yttrium is classified as a light rare earthelement due to its lower atomic weight.

As used herein, the terms “light rare earth elements” and “LREE” can beused interchangeably and refer to scandium, lanthanum, cerium,praseodymium, neodymium, promethium, samarium, and europium. In someaspects, these designations may differ slightly but are generally basedon atomic weight.

As used herein, the term “total rare earth elements” and “TREE” can beused interchangeably and refer the total REE present in a disclosedcomposition or product of a disclosed process, method, or device,wherein the REE comprises

“Critical minerals” (CM) as used herein include minerals important tonational security and the economy. REEs are considered critical mineralsdue to their numerous industrial uses. Other critical minerals may alsobe purified and concentrated using the disclosed process including, butnot limited to, cobalt, gallium, germanium, hafnium, indium, niobium,rhenium, rubidium, tantalum, and tellurium.

As used herein, “gangue” metals and other materials are undesiredmaterials that surround or are co-located with the REEs being isolatedand concentrated by the disclosed process. In one aspect, in the presentprocess, gangue material can include, but is not limited to, aluminum,calcium, magnesium, manganese, silicon, chloride, and the like. In someaspects, gangue materials may have little or no economic value. In otheraspects, gangue materials may have industrial uses but their presencealongside more valuable REEs can complicate the recovery of the REEs.

“Acid mine drainage” (AMD) as used herein refers to acidic water thatoutflows from mines such as, for example, metal mines or coal mines. Inone aspect, AMD intensifies in scale and scope when construction,mining, and other activities that disturb the earth occur in and aroundrocks containing sulfide minerals. AMD can have high concentrations ofmetal ions that can cause detrimental effects to aquatic environments,especially in combination with low pH. AMD from coal mines and othersources often contains trace amounts of REEs, as well. “Acid minedrainage” as understood within the definition herein can be aqueouseffluent from mining operations, mill tailings, overburden from miningoperations, excavations, acid process waste streams, seepages, and otheraqueous flows having elevated levels of metal ions and/or anions. Acidmine drainage is characterized by the presence of metals such as iron,manganese, aluminum, cadmium, cobalt, copper, lead, magnesium,molybdenum, nickel, zinc, and others. Acid mine drainage may alsoinclude undesirable anions such as sulfate, fluoride, nitrate andchloride. As used in the present application, “mine” is understood tomean active, inactive or abandoned mining operations for removingminerals, metals, ores or coal from the earth. Environmental regulationspromulgated by the Environmental Protection Agency under CAA, RCRA, andCERCLA, as well as those promulgated by state and local authorities,mandate that the concentration of certain minerals and metals inspecific aqueous effluents be less than the established regulatorylevels.

“AMD precipitate” (AMDp) as used herein refers to a byproduct of AMDtreatment. In one aspect, AMDp contains REEs but may also contain ganguemetals such as, for example, iron and aluminum. In one aspect, AMDpcontains from about 0.06% to about 0.1% REE. As used herein, “enrichedAMD precipitate” (eAMDp) refers to an AMD product having from about 0.1%to about 5% REE on a dry weight basis. In another aspect, eAMDp has alower gangue metal content then AMDp.

A “feedstock” as used herein is a raw material processed to recover REEsand other valuable components (e.g., CMs). A feedstock may be too toxicto release into the natural environment and, in one aspect, thedisclosed process can remove commercially valuable components from thefeedstock while simultaneously rendering the feedstock suitable forenvironmental release.

As used herein, “pregnant leach solution” (PLS) is water with an acidicpH and a high metal content. In one aspect, PLS can be processed usingseveral purification technologies including, but not limited to, solventextraction, ion exchange resins, selective precipitation, and fractionalcrystallization to remove and/or concentrate the metals. In someaspects, PLS may have a high solids content and may require filtrationprior to further processing.

“Raffinate,” meanwhile, refers to a product of chemical separation,wherein one or more components have been removed. In one aspect,following solvent extraction as disclosed herein, raffinate is theaqueous component depleted in REE content. In another aspect, raffinatecan include undesired gangue material.

As used herein, “GEOTUBE®” refers to a dewatering device made from apolypropylene fabric that can be produced according to the needs of aparticular project or industry. In one aspect, sludge or other materialto be separated is pumped into a GEOTUBE® container and a fabric linerkeeps solids trapped inside while filtrate water escapes and can bedirected to a treatment facility.

Unless otherwise specified, temperatures referred to herein are based onatmospheric pressure (i.e., one atmosphere).

Acronyms.

The following acronyms as follows are used herein throughout. It isunderstood that the fully written phrase or textual description can beused interchangeably with the acronym without changing the intendedmeaning.

ACRONYM BRIEF DESCRIPTION

-   -   AL Acid Leaching    -   ALSX Acid Leaching/Solvent Extraction    -   AMD Raw Acid Mine Drainage    -   AMDp Precipitate formed from AMD    -   CM Critical Minerals    -   HPC Hydraulic Pre-Concentrate    -   HREE Heavy Rare Earth Element    -   HREO Heavy Rare Earth Oxide    -   ICP-MS Inductively Coupled Plasma Mass Spectrometry    -   ICP-OES Inductively Coupled Plasma Optical Emission Spectrometry    -   LREE Light Rare Earth Elements    -   LREO Light Rare Earth Oxide    -   MREO Mixed Rare Earth Oxide    -   NPDES National Pollution Discharge Elimination System    -   OA Oxalic Acid    -   PC Pre-Concentrate    -   PLS Pregnant Leach Solution    -   PVDF Polyvinylidene fluoride    -   RE or REE Rare Earth or Rare Earth Element    -   REE/CM Rare Earth Element/Critical Mineral

ACRONYM BRIEF DESCRIPTION

-   -   REEF Rare Earth Extraction Facility    -   SX Solvent Extraction    -   WVU West Virginia University    -   WVDEP West Virginia Department of Environmental Protection        Production of REE/CM from AMD—Multi-Modular Approach.

In various aspects, the present disclosure relates to the variousmodules or process components that can be utilized in geographicalseparated components to provide production of REE/CMs from an AMDfeedstock material. Disclosed herein are various processes and methodsfor enrichment of REE/CMs from AMD, while at the same time removingmaterials deleterious or inhibitory to downstream processing steps.

The processing of AMD, as disclosed herein, can yield a HPC that isenriched in REE/CMs, and then further processed to a conditioned HPC.The HPC or conditioned HPC is in a form that can be easily transportedto a site that may be geographically distant (or used on-site orfacility proximal to the AMD site) for further process to provide a PLS.The PLS can be stored and then transported to a proximal productionfacility or geographically distant facility for further process andenrichment via solvent extraction, thereby yielding MREOs. Solventextraction can be carried out by any means of solvent extraction knownto the skilled artisan utilizing the disclosed PLS (e.g., see Xie, F.,et al., “A critical review on solvent extraction of rare earths fromaqueous solutions.” Minerals Engineering 56 (2014) 10-28).

The MREOs can then be reduced to elemental rare earth metals. Thepresent disclosure relates to each of these modules, which can beoperated as discrete modules utilizing an input feedstock and providingan output material that can be used in a subsequent step. The presentdisclosure relates to each of these modules, processes or stepsindividually and linked to one another by utilizing the output materialof one module or process as feedstock in the next module or process.

In various aspects, MREOs can be in the form of metal carboxylates,e.g., metal oxalates, which can be utilized in a module or process ofreduction, e.g., as disclosed in U.S. Pat. Publ. No. US 2020/0047256,which is incorporated herein in its entirety as relates to manufactureof fine metal powders from metal carboxylate compounds such as metaloxalate compounds.

In a further aspect, MREOs can be utilized in an electrowinning orelectrolytic process, e.g., a molten salt electrolysis process (forexample, see Chamber, M. F. and Murphy, F. E. “Molten Salt Electrolysisof Neodymium from a Chloride Electrolyte.” The Minerals, Metals andMaterials Society (1988): 369-376; Krishnamurthy, N., and C. K. Gupta.“Rare Earth Metals and Alloys by Electrolytic Methods.” MineralProcessing and Extractive Metallurgy Review 22.4 (2002): 477-507; andSiming, Pang, Yen Homer Shih Hung, Li Zongan, Chen Dehong, XuliHai, andZhao Bin. “Preparation of Molten Salt Electrolysis of Rare Earth Metalsand Their Alloys Technology Progress.” Chinese Journal of Rare Metals35.3 (2011): 440-50; each of which is incorporated herein).Alternatively, a metallothermic reduction process can also be utilizedto further process MREOs.

It should be noted that FIGS. 26A-26B show diagrams of an apparentlyintegrated system that may occur on a single site or at discretelocations within a single site. However, the various steps discretelydescribed in FIGS. 25A-25B, and shown diagrammatically in FIGS. 26A-26B,can be aggregated into subsystems or subprocesses to form separableproduction sites and subprocesses. In one aspect, the overall processdiagrammatically shown in FIG. 26A is shown as four separatesub-processes in FIG. 27A labeled as Sites #1-4. It is understood thatSite #1 may be operated discretely in a location distinct from Sites#2-4, and the output of Site #1 transported for use at Site #2.Similarly, the output of the steps comprising Site #2 may be transportedto a discrete Site #3. In a further aspect, the overall processdiagrammatically shown in FIG. 26B is shown as four separatesub-processes in FIG. 27B labeled as Sites #1-4.

In various aspects, Site #1 (AMD localization) is a location that theREE Elements and Critical Materials are contained in the AMD thatemanates from or on the ground (mine site, seep area, mine portal). Thisliquid can be treated at the location, can be pumped/piped to atreatment site, or hauled (drum, tanker truck, railcar, or othertransportation means) to the next process at Site #2.

In a further aspect, Site #2 (Neutralization Facility—PreconcentrateGeneration) can be located at or near Site #1 where the AMD liquid is pHadjusted up (base addition) to separate the gangue materials from theREE/CMs with at least two individual pH set points. The pH adjustmentscan be initiated at or near Site #1 or can be done distally from Site#1. These pH adjustments can be accomplished in rectangular or circularclarifiers or other apparatuses such as thickeners. Site #2 canencompass at least two clarifiers noted as Clarifier #1 and Clarifier#2. Clarifier #1 can produce a sludge (gangue) at the first pH setpoint. The solid material is separated from the liquid via gravity. Thisunit can have a polymer flocculant added to facilitate the gathering ofthe created solids which helps the solids materials to fall to thebottom in a timely manner. Clarifier #2 is fed additional base materialto raise the pH set point of the influent supernatant from Clarifier #1.This pH adjustment takes the REE's and CM materials and creates a PC forthe REE's and CM's to be concentrated and processed. Polymer flocculantmay be added to help gather the PC in to large floc particles which aidsin gravity settling. The supernatant water is released to theenvironment as clean treated water. The solid visible material containsthe REE and CM product. This material can be gathered and delivered toSite #3. The solid material is the HPC.

In a further aspect, Site #3 (HPC Conditioning) receives material fromSite #2. Site #3 can be located at or near Site #2 or can be transportedto site 3 by drums, trucks or pumps/pipelines. Material in this step isconditioned by dewatering to increase the percent solids of the HPC.Dewatering can be completed by gravity settling in a series of conebottom tanks or by placing the HPC in geobags. As discussed above, in anaspect, the HPC material can be placed in a primary conditioning conetank. This will separate the solids from the liquids over a short periodof time (approx. 1 hour). The supernatant can be drawn off the tank(s)with the liquid reporting for discharge from the site as clean water.The conditioned HPC material from the multiple primary tanks can becombined in a secondary conditioning tank(s) and the supernatant removalprocess repeated. The process increases the % solids of the HPC. Thematerial can be transported to Site #4 via drum(s), tanker truck(s) orpump/pipeline. Alternatively, as discussed above, the HPC material fromSite #2 is placed into a number of geobags. The geobag allows the waterto decant through the designed bag leaving the HPC solids retained inthe geobag. The geobags allow the material to continue to decant thusincreasing the HPC % solids over time. When the material dries to anacceptable percent solids for future processing, the bag is cut open andthe material transported to Site #4. The material can be transported indrums, roll off containers or trucks.

In a further aspect, Site #4 (PLS (Acid Leaching) Generation) can be ator near Site #3 or can be at a different location. The material fromSite #3 is placed in the PLS tank to be acid leached. Acid is added tothe material as it is being placed in the tank. A mixer is utilized tomake a homogeneous product. When the product is mixed sufficiently, themixer is stopped and a polymer flocculant is added to allow theresiduals to settle. The initial liquid PLS material is drawn off thetank, filtered and placed in the neutralization tank for furtherprocessing. A base is added while mixing. Upon sufficient mixing, apolymer flocculant is added to expedite the residual settling. Thesupernatant (PLS) is drawn from the tank and placed in a tank. This tankcould consist of tanks, drums, trucks, or pipeline for furtherprocessing through the Solvent Extraction process (Site #5).

As discussed herein throughout, following or concomitant with various pHadjustment steps, a flocculent or coagulant may optionally be includedin the process. That is, the disclosed processes contemplate further useof polymer chemical type additives to flocculate aqueous effluentsdescribed herein. In some instances, the flocculent can be a polymerflocculent, e.g., a cationic emulsion polymer, having a medium chargedensity range of from about 40% to about 60%, a linear structure, and amedium molecular weight. Suitable cation emulsion polymer flocculantscan have a specific gravity of from about 1.02 to 1.07 and an averagenon-volatile solids concentration between 30 to 45%. The bulk pH rangeof such cationic emulsion polymers can be from about 6 to about 8 and aviscosity of between about 1000 to about 3000 (cps). In use, thecationic emulsion polymer can be injected into the first stage effluentat a concentration range of 1 ppm to 40 ppm, and with a target residentreaction time of about 4 to 15 minutes.

In various aspects, raw, untreated, AMD can be conveyed to a treatmentunit which includes a base chemical addition (hydrated lime solution) toadjust the water up to between 4.0 and 5.0 pH. The treatment unit can bea pond or a fabricated unit (round or rectangular shaped) that allowstime to settle the particles via gravity after the base addition.Mechanical or chemical oxidization steps can be included to convert allferrous ions to ferric (if needed). The oxidation process can be donewith aeration (natural or mechanical) or chemical additions such ashydrogen peroxide. The raw water can be collected in a pond or otherstructure. The raw water can be brought to the plant and initialtreatment can occur in a rapid mix tank where the base addition (such ashydrated lime or caustic soda solution) and polymer flocculent(optionally provided as appropriate for flocculation) is added. A rapidmixing device can be used to mix the base material with the raw water inorder to obtain pH homogeneity. For example, this can be donemechanically with a paddle mixer or a tank eductor under pump pressureand volume. The water can enter a slow mix tank to allow particles tocoagulate, thereby allowing flocked particles to grow in size and aidingsettling of the solids. If a polymer flocculent is utilized, it isrecommended that the specific polymer flocculent be jar tested on thespecific water to be treated. The fluid from the slow mix tank can beintroduced to a first clarifier, or alternatively, a settlement basin oranother means of separating the liquid and solid fractions via gravitymay be utilized, e.g., geobags as disclosed herein. Over a suitableperiod of time, particles settle to the bottom of the clarifier or othersettlement system. The solid fraction thus obtained contains largelyamounts of gangue metals which are dispatched to a disposal facility.

In various aspects, secondary AMD treatment can be carried out of theforegoing decant solution separated from particles. For example, thedecant solution from the preceding step can be transferred to a secondAMD treatment unit with the same design as described above. Additionalbase (hydrated lime solution) can be added to raise the pH of the decantsolution to a pH range between about 7.5 and about 8.5 depending on theneed to segregate the critical materials. Polymer flocculant can beadded to facilitate particle agglomeration and settlement if needed. Thesame mixing process as described in the preceding paragraph can be usedto prepare the solution for settling, and this provides forprecipitation of REE, cobalt and other critical minerals as well asresidual gangue metals to form hydraulic pre-concentrate (HPC). HPCconsists of a slurry of fine floc containing both REE/CM and ganguesuspended in water; solids are in the range of 0.1 to 1% on a massbasis. HPC is then collected in a settlement basin or clarifier whiledecanted water is dispatched to the approved discharge point.

In various aspects, HPC produced in the foregoing steps can be directedto a series of cone bottom “primary conditioning tanks.” Theconditioning tank(s) can be made of any suitable material, e.g., plastictanks or plastic lined tanks resistant to high or low pH can be used.Specific height, width and capacities of the tanks will be site and flowspecific as determined by the operator. In a further aspect, the conebottom tanks comprise a cylindrical section above a conical section. Theconical sections of the tanks can be manufactured in 15, 30, 45 and 60degree angles from horizontal. Any of the conical angles are acceptableas the HPC will be in a slurry form and is believed to be able toreadily flow. The top of the tank can comprise an opening to permitpersonnel access and tank cleaning or the tank can be an open topdesign. The cone bottom tanks can be designed to separate by gravitysolid and liquid fractions of a slurry and funnel the settled materials(HPC) to a port for easy gathering. Gravity can separate the solids fromthe liquid with the solids falling through the liquid to make a solidsfree supernatant. The HPC from the second clarifier can be pumped in thetop of the tank, while a lateral port(s) near the bottom of thecylindrical section allows withdrawal of supernatant and a port at thebottom of the conical section permits withdrawal of the settled solidscomprising the HPC. The primary conditioning tanks can be sized andarranged to accommodate the HPC from a second clarifier treatment step.

In various aspects, a cone tank, i.e., a primary conditioning cone tank,can be hydraulically filled with a HPC slurry produced as describedherein above. Briefly, a polymer flocculent can be added to accelerateHPC settlement. When the gravity settling is completed after a suitableperiod of time, e.g., 30 to 75 minutes, but dependent on tank volume andtank wall height, supernatant water can be decanted from a lateralport(s) above the cone portion and discharged. The foregoing process canreduce HPC volume by approximately 60-85%. The filling process canrepeated in a plurality of conditioning tanks in a treatment train. Thenumber of tanks required in the treatment system can designed tomaximize HPC capture. The foregoing process provides a first conditionedHPC, i.e., the settled bottom tank material formed in the immediatelypreceding process.

In various aspects, the primary conditioned HPC can be utilized in thepreparation of a second conditioned HPC. For example, the port on thebottom of each primary conditioning cone tank can opened after HPCsettlement and the HPC material can be hydraulically transferred toanother set of tanks, i.e., secondary conditioning cone tanks. Aftertransfer of the HPC from the primary tanks, the ports are closed and theprocess of filling and settling is repeated as described above for theprimary conditioning cone tank, including optionally providing aflocculent. The secondary conditioning cone tank(s) can gather theprimary conditioned HPC from the primary conditioning tanks and furtherreduce the water in the slurry via gravity separation.

In various aspects, the secondary conditioning tank(s) receives theconditioned HPC material from the primary cone tank decant. This tank(s)gathers the conditioned HPC from the primary conditioning cone tanks toremove additional decantable water. When this conditioned HPC settles,the supernatant is decanted from the tank from the lateral port as wasdone in the primary cone tank. The conditioned HPC from this secondarycone tank train can hydraulically transported to an open top mix tank(s)for PLS generation. The process of primary and secondary decanting ofthe entrained water is repeated until sufficient conditioned HPC isplaced in the PLS generation tank.

In various aspects, the method for preparation of the PLS can be carriedas described herein below. Briefly, conditioned (primary or secondaryconditioned) HPC can be mixed in a mixing structure, e.g., a vat orplastic tank, with a suitable amount of a suitable acid, e.g., nitric,sulfuric, and/or hydrochloric acid, such that the amount of acid addedforms a solution with the pH in the range about 2.5 to about 3.5. Thesolution is mixed while adding the acid. After the pH stabilizes for aperiod of a time, e.g., about 30 minutes, a polymer flocculant canoptionally be added to facilitate settling of particles. Upon settling,the supernatant form can be hydraulically pumped to a PLS NeutralizationTank and filtered, e.g., using a bag filter. The settled precipitatescan also be filtered through a bag filter to recover the remainingaqueous PLS and the residuals discarded. The foregoing leaching processprovides for dissolution of the HPC and creates an enriched solutioncomprising REE, other critical materials and residual gangue metals.Multiple charges of conditioned HPC can be added to the PLS tank withsufficient additional acid to maintain the desired pH (2.5-3.5). TheREE/critical material concentration reaches a range of 1-10%.

In various aspects, the PLS can be neutralized using a base such ashydrated lime or caustic soda. The base is added to the PLS generated inthe foregoing step in an amount sufficient to raise the pH to about4.0-4.5. Base is added with mixing. Upon pH stabilization, polymerflocculant can optionally be added with mixing. Mixing is thenterminated, and the solution allowed to settle. The neutralized PLS canbe filtered in a bag filter and stored. The resulting filtrate is thenready for introduction to a solvent extraction circuit or otherpurification means.

In a further aspect, REE/CM can alternatively be captured at small orremote AMD treatment sites using passive filtration media such as ageobag or filtration bag. In some aspects, the alternative can beutilized at sites with limited electrical power and/or where the AMDdischarge rate does not justify a mechanized AMD treatment plant asdescribed above. Under this alternative approach, the pH of the raw AMDcan be raised to between 4.0 and 5.0 using a base such as hydrated limeor caustic soda and the resulting precipitated gangue can be captured ina pond or other type of settlement structure. The supernatant from thisfirst treatment step can then be directed a separate pond or settlementstructure and treated to raise the pH to 7.5 to 8.5 by addition of abase such as hydrated lime slurry or a caustic soda solution. The pHadjusted supernatant can be directed into a parallel array ofspecifically designed geobags or filtration bags to capture the finelydispersed, solid REE/CM materials. As the captured precipitate fillseach filtration bag can be taken offline and allowed to dewater and airdry to a solids content of between 20-80%. Upon reaching the desiredsolids content, the HPC thus formed be transported to a REE processingplant, e.g., via truck or rail. The filter cake can then be processedinto PLS as described immediately below.

In various aspects, the filter cake produced in the immediatelypreceding step can be crushed and soaked in a strong acid, e.g.,hydrochloric acid (about 6 to 12M). The ratio of filter cake tohydrochloric acid can be about 1-2 liters of hydrochloric acid per 1 kgof filter cake (dry weight basis). Additional water can be added to theforegoing, e.g., about 10-30 liters of water per 1 kg of initial filtercake material. This solution can be further processed as describedherein above, e.g., conditioning and/or preparation of PLS.

The PLS can be further processed, e.g., neutralized as described above.The neutralized PLS can be used as a feedstock for solvent extraction asdescribed herein.

In a further aspect, PLS carbonate material can be prepared after theabove-described PLS neutralization. Briefly, the pH of supernatant fromthe PLS neutralization process can be adjusted to about 8-9, e.g., pH8.5, by addition of a suitable carbonate base, e.g., calcium carbonateor sodium carbonate, with mixing. Optionally, polymer flocculant can beadded with mixing to facilitate slurry settling. The mixer isterminated, and the carbonate formed is allowed to settle. The mixed PLScarbonate precipitate comprising REE/CM can be recovered for furtherprocessing. The raffinate (or supernatant) that is drained from thecarbonate tank can be further processed to recover the cobalt, manganeseand nickel via solvent extraction. The residual and remaining raffinatecan filtered with the carbonate REEs retained on the filter media. Thefiltrate can be added to the raffinate for further processing ofcritical minerals via solvent extraction.

In a further aspect, PLS oxalate can be prepared from the PLS preparedas described herein above. Briefly, oxalic acid can be added to PLS toselectively precipitate a mixed REE oxalate product. The pH of thesupernatant from the PLS process is lowered by addition of oxalic acid(about 15 g/L to about 25 g/L) with mixing. The pH of this solution isthen raised while mixing with ammonium hydroxide to plus 1.5 pH pointsabove the initial solution pH after the oxalic acid addition. The mixeris turned off to facilitate settling for a suitable period of time,e.g., about 30-120 minutes. Upon settling, the solution's supernatantcan be removed, e.g., decanted, from the tank and the remaining solutionfiltered to gather the precipitated REE oxalate. The filtrate can beutilized for further processing to recover cobalt, manganese and nickelthrough solvent extraction. The precipitated REE oxalate can becalcined, e.g., at about 1000-1500° C. fora suitable period of time,e.g., about 1-12 hours. The REE oxalate solid thus obtained can besequentially washed with a mild acid solution, e.g., a mild nitric acidsolution, and water to remove carbonates and other impurities. Theproduct is a mixed REE oxide.

Process for an Enriched Pregnant Leach Solution from Acid MineDischarge.

In one aspect, the present disclosure relates to processes for providinga PLS enriched in REE materials or REE/CM materials, in which thefeedstock for the process is an acid mine discharge (“AMD”) feedstock.In a further aspect, the PLS can be utilized, as disclosed herein, in asolvent extraction process, or other suitable purification technology,as disclosed herein, and to obtain one or more REE that is furtherpurified or enriched.

Disclosed herein are methods for preparing a hydraulic pre-concentrateenriched in rare earth elements and critical minerals, the methodcomprising: (a) contacting a raw material with a first base in an amountsufficient to adjust the pH to a value from about 4.0 to about 6.0,thereby forming a mixture comprising a first aqueous phase and a firstsolid concentrate; (b) separating the first aqueous phase from the firstsolid concentrate; (c) contacting the first aqueous phase with a secondbase in an amount sufficient to adjust the pH to a value from about 7.0to about 9.0, thereby forming a mixture comprising a second aqueousphase and the hydraulic pre-concentrate; (d) removing the second aqueousphase and collecting the hydraulic pre-concentrate; wherein the rawmaterial comprises rare earth elements; and wherein the hydraulicpre-concentrate is enriched in rare earth elements.

Also disclosed herein are methods for preparing a pregnant leachsolution, the method comprising: transferring a disclosed firstconditioned hydraulic pre-concentrate or a disclosed second conditionedhydraulic pre-concentrate to a mixing tank; and adding a first acid tothe mixing tank in an amount sufficient to adjust the pH from about 2.0to about 4.0, thereby forming the pregnant leach solution; wherein thefirst acid is mixed with the first conditioned hydraulic pre-concentrateor the second conditioned hydraulic pre-concentrate as the first acid isadded.

Also disclosed herein are methods for preparing a pregnant leachsolution, the method comprising: transferring a hydraulicpre-concentrate to a mixing tank; and adding a first acid to the mixingtank in an amount sufficient to adjust the pH from about 2.0 to about4.0, thereby forming the pregnant leach solution; wherein the hydraulicpre-concentrate is enriched in rare earth elements compared to the rareearth elements concentration present in an acid mine discharge; andwherein the first acid is mixed with the hydraulic pre-concentrate asthe first acid is added.

Also disclosed herein are methods for making a rare earth element oxide,the method comprising the steps of: providing a rare earth element oxidefeedstock material; subjecting the rare earth element oxide feedstockmaterial to one or more solvent extraction steps; and isolating the rareearth element oxide from the one or more solvent extraction steps;wherein the rare earth element oxide feedstock material comprises adisclosed hydraulic pre-concentrate, a disclosed pregnant leachsolution, or combination thereof.

Also disclosed herein are methods for making a rare earth element oxide,the method comprising the steps of: providing a rare earth element oxidefeedstock material; subjecting the rare earth element oxide feedstockmaterial to one or more solvent extraction steps; and isolating the rareearth element oxide from the one or more solvent extraction steps;wherein the rare earth element oxide feedstock material comprises ahydraulic pre-concentrate, a pregnant leach solution, or combinationthereof.

In a further aspect, the disclosed processes comprise the followingsteps: (1) transfer raw AMD feedstock to a separator; (2) aeratefeedstock and add an effective amount of at least one base to theseparator to raise the resultant mixture pH; (3) optionally add aneffective amount of one or more flocculating and/or coagulating agent;(4) separate solid and aqueous phases, and discard solids; (5)optionally, if recovering scandium, transfer the aqueous phase from thepreceding step to a separator and add an effective amount of base toraise resultant solution pH, followed by (5)(a) optionally, add aneffective amount of coagulating and/or flocculating agents; and then,(5)(b) separate solid and aqueous phases and collect Sc-enriched solidconcentrate; (6) transfer the aqueous phase from step (4) or fromoptional step (5) to a separator; (7) add an effective amount of atleast one base to raise resultant mixture pH; (8) optionally add aneffective amount of one or more flocculating and/or coagulating agent;(9) discharge effluent and collect REE-enriched pre-concentrate; (10)dewater pre-concentrate and transfer dewatered REE-enrichedpre-concentrate to a mixer; (11) add an effective amount of at least oneacid to lower resultant solution pH, and optionally add an effectiveamount of one or more oxidizing agents; (12) optionally add an effectiveamount of one or more flocculating and/or coagulating agent; (13)transfer resultant solution to from the preceding step a filtrationapparatus, filter, and discard residual solids retained by the filter;(14) transfer resultant filtrate solution from the preceding step to amixer; (15) add an effective amount of at least one base to raiseresultant solution pH; (16) transfer resultant solution to a filtrationapparatus, filter, and discard residual solids retained by the filter;and (17) the resultant PLS may be stored. In a further aspect, the PLSmay be utilized in a solvent extraction process, or other suitablepurification technology, as disclosed herein, and to obtain one or moreREE that is further purified or enriched.

FIG. 23 shows a flow diagram of an exemplary process to produce a PLS asdisclosed herein. The plant includes a means 700 for transferring rawAMD feedstock to a separator and a means 702 for adding base to raisethe resultant solution pH to from about 4 to about 4.5 as well as ameans 704 for adding flocculating agents if necessary and a means 706for separating solid and aqueous phases and for discarding solids. Ifscandium recovery is performed, an optional scandium recovery device 708is incorporated at this stage. The scandium recovery device 708 includesa means 710 for transferring the aqueous phase to a separator, a means712 for adding enough base to raise the resultant solution pH to fromabout 4.5 to about 5, a means 714 to add optional flocculating and/orcoagulating agents, and a means 716 for separating solid and aqueousphases and collecting a scandium-enriched solid concentrated. Theresultant material from this step or by a separation means 706 ifscandium recovery is not performed is transferred to separator 718. Ameans 720 for adding base to the separator 718 dispenses base untilsolution pH is from about 8.0 to about 8.5, while a means 722 addsoptional flocculating and/or coagulating agents and a device 724discharged effluent for standard water treatment while collecting anREE-enriched preconcentrate for further processing. REE-enrichedpreconcentrate is transferred to a mixer by a mechanism 726 and a means728 for adding acid dispenses acid to lower the solution pH to fromabout 0.1 to about 2.0, in a further aspect lower the solution pH tofrom about 0.3 to about 1.1, in a further aspect lower the solution pHto from about 0.5 to about 0.8, in a further aspect lower the solutionpH to about 0.7, while a means 730 adds optional flocculating agents.Acidified solution is transferred by device 732 to a filter and residualsolids are discarded. A means 734 transfers the resultant solution to amixer where a base dispensing a means 736 dispenses base until thesolution pH is from about 2.8 to about 3.0. A device 738 then transfersthe resultant solution to a filter, wherein residual solids arediscarded. Following this, a PLS is stored in storage by a means 740until transferred to solvent extraction by a transfer means 742.

FIG. 24 shows a diagram of a plant that can produce a PLS according tothe process in FIG. 23 or another exemplary process as disclosed herein.Raw AMD feedstock 800 is transferred to a first separator 810, whereinthe separator is connected to a base storage unit 812 and a flocculantstorage unit 814 that can dispense base and flocculant as needed intothe separator 810; solids 816 that precipitate at this point includemostly iron and aluminum and are transferred for waste disposal orfurther processing as desired. If scandium recovery is performed, theliquids from the first separator 810 are transferred to a secondseparator 820, which is also connected to a base storage unit 822 and aflocculant storage unit 824 that can dispense base and flocculant asneeded according to the process disclosed herein. Scandium precipitatesfrom the second separator 820 as a scandium-enriched solid concentrate826 and the remainder of the material still containing significant REEsis passed to a third separator 830. If scandium is not collected,REE-containing material is passed from the first separator 810 directlyto the third separator 830. The third separator 830 is connected to basestorage unit 832 and flocculant storage unit 834 that can dispense baseand flocculant as needed into the third separator 830; effluent fromthis process 838 is discharged from the system and the REE-enrichedsolid pre-concentrate 836 produced by this process is transferred to afirst mixer 840, wherein the mixer is connected to an acid storage unit842 that can dispense acid into the mixer 840 as needed to control thepH of the solution as disclosed herein. Material passes from the mixer840 to a first filter 850 wherein leach residue 852 is separated fromliquid material that is then transferred to a second mixer 860 that isconnected to a base storage unit 862 that can dispense base into themixer 860 as needed. From mixer 860 liquids are passed to a secondfilter 870 and leach residue 872 is discarded while filtrate istransferred as PLS to storage unit 880 for later use in solventextraction procedures 882.

In one aspect, feedstock useful in step 1 can include raw AMD. In afurther aspect, distribution of REE and major elements in 155 AMDsources in the Central Appalachian coal basin AMD source (CAPP) andNorthern Appalachian coal basin AMD source (NAPP) are provided in Table3 below.

TABLE 3 Distribution of REE and Major Elements in Appalachian AMDSources. Confidence Number of CI:Mean Mean Interval Samples Ratio CAPPAMD REE (μg/L) Sc 3.12 1.12 49 0.36 Y 50.48 20.53 51 0.41 La 27.27 15.2151 0.56 Ce 54.55 27.65 51 0.51 Pr 8.16 3.95 50 0.48 Nd 37.82 17.19 510.45 Sm 9.88 4.04 50 0.41 Eu 2.68 0.98 50 0.37 Gd 12.59 4.95 51 0.39 Tb1.98 0.71 50 0.36 Dy 10.76 4.31 50 0.40 Ho 1.98 0.73 50 0.37 Er 5.082.09 50 0.41 Tm 0.82 0.25 49 0.30 Yb 3.95 1.58 50 0.40 Lu 0.72 0.21 490.29 TREE 231.85 103.12 50 0.44 HREE 91.48 LREE 140.36 Median 6.62 3.0250 0.40 Major Metal (mg/L) Influent pH 4.95 0.43 51 0.09 Al 13.23 5.2151 0.39 Ca 169.84 27.19 51 0.16 Fe 19.06 13.09 10 0.69 Mg 126.06 26.8651 0.21 Mn 10.93 3.37 51 0.31 Na 37.37 18.89 51 0.51 Si 11.06 2.27 510.21 Cl 5.40 2.94 50 0.54 SO₄ 1111.84 193.95 50 0.17 TMM 1504.77 293.7851 3.19 Median 19.06 13.09 51 0.31 NAPP AMD REE (μg/L) Sc 6.34 1.55 1310.24 Y 80.54 23.92 134 0.30 La 21.09 6.69 134 0.32 Ce 63.15 19.09 1340.30 Pr 9.79 2.81 133 0.29 Nd 45.84 13.15 134 0.29 Sm 13.25 3.57 1330.27 Eu 3.78 1.02 131 0.27 Gd 18.54 5.17 134 0.28 Tb 3.13 0.83 132 0.26Dy 16.94 4.79 133 0.28 Ho 3.28 0.89 132 0.27 Er 8.28 2.40 133 0.29 Tm1.28 0.30 130 0.23 Yb 6.36 1.79 134 0.28 Lu 1.08 0.25 130 0.23 TREE302.69 85.99 133 0.28 HREE 145.79 LREE 156.90 Median 9.03 2.60 133 0.28Major Metal (mg/L) Influent pH 4.21 0.34 132 0.08 Al 22.98 4.82 134 0.21Ca 176.68 22.57 134 0.13 Fe 61.05 22.15 134 0.36 Mg 75.34 10.71 134 0.14Mn 9.43 2.42 134 0.26 Na 519.65 185.99 134 0.36 Si 14.23 1.64 134 0.12Cl 304.07 239.70 130 0.79 SO₄ 1704.43 337.54 130 0.20 TMM 2887.85 827.54133 2.56 Median 75.34 22.15 134 0.21

In a further aspect, feedstocks with the compositional ranges in Table 3are useful in the process disclosed herein. In one aspect, AMD can bethe feedstock for the disclosed process; however, other feedstocks arealso contemplated. In one aspect, the feedstocks useful herein do notinclude high levels of uranium, thorium, or other hazardous components.

In one aspect, the process disclosed can utilize an AMD feedstock with apH of from less than 2 to less than about 5.5, or of about less than 2,2.5, 3, 3.5, 4, 4.5, 5, or 5.5. In one aspect, the feedstock pH is lessthan 3. In another aspect, the feedstock pH is less than 2. A typicaldistribution of AMD REE concentrations as a function of pH can be seenin FIG. 22 .

In one aspect, in step 2 as disclosed above, an effective amount of atleast one base is an amount sufficient to raise the resultant mixture pHto about 4 to about 4.5, or at least about 4, 4.1, 4.2, 4.3, 4.4, orabout 4.5, or a combination of any of the foregoing values, or a rangeencompassing any of the foregoing values. In a further aspect, the basecan be NaOH, KOH, ammonia or ammonium hydroxide, calcium pellets,quicklime, lime slurry, or a combination thereof. In one aspect, thebase is lime slurry.

In a further aspect, in step 4 as disclosed above, the discarded solidscan comprise iron or aluminum and/or other gangue metals with similarchemical and physical properties.

In one aspect, if scandium is being recovered and step 5 in thedisclosed process is being performed, when base is added, the desiredresultant pH can be from about 4.9 to about 5.1, or about 4.9, 5.0, orabout 5.1, or a combination of any of the foregoing values, or a rangeencompassing any of the foregoing values. In a further aspect, the basecan be NaOH, KOH, ammonia or an ammonium compound, calcium pellets,quicklime, lime slurry, or a combination thereof. In one aspect, thebase is lime slurry.

In one aspect, in step 7 as disclosed above, an effective amount of atleast one base is an amount sufficient to raise the resultant mixture pHto about 8 to about 8.5, or at least about 7.8, 7.9, 8, 8.1, 8.2, 8.3,8.4, 8.5, 8.6, or about 8.7, or a combination of any of the foregoingvalues, or a range encompassing any of the foregoing values. In afurther aspect, the base can be NaOH, KOH, ammonia or ammoniumhydroxide, calcium pellets, quicklime, lime slurry, or a combinationthereof. In one aspect, the base is lime slurry. In one aspect, a higherpH from within the disclosed range may aid in recovering additionalcobalt.

In one aspect, in step 11 as disclosed above, the desired resultant pHis from about 0.5 to about 3.2, or is about 0.5, 0.6, 0.7, 0.8, 0.9, 1,1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5,2.6, 2.7, 2.8, 2.9, 3, 3.1, or about 3.2, or a combination of any of theforegoing values, or a range encompassing any of the foregoing values.In some aspects, pH in this step can be chosen based on economicconsiderations such as, for example, sales value of product versus costof acid added in this step. In another aspect, various acids arecontemplated in this step including, but not limited to, sulfuric acid,nitric acid, hydrochloric acid, or a combination thereof. In one aspect,the acid is nitric acid. In another aspect, the acid is hydrochloricacid.

In a further aspect, acid contact with the feedstock, raw material, orAMDp/eAMDp preconcentrate occurs in a reactor that is open to theatmosphere. In another aspect, this step can be conducted at roomtemperature. In a still further aspect, prior to acid addition, thefeedstock, raw material, or AMDp/eAMDp preconcentrate can be contactedwith water while mixing to create a slurry. In a yet further aspect, theslurry is mixed with acid in step 11 as described above with continuousmixing to dissolve the REEs out of the solid feedstock.

In a further aspect, as noted above, optionally step 11 can furthercomprise addition of an oxidizing agent. In a still further aspect, thestep 11 comprises the addition of an oxidizing agent, such that thisaspect is not an optional aspect. In a still further aspect, theoxidizing agent can be hydrogen peroxide. Without wishing to be bound bya particular theory, it is believed that the addition of an oxidizingagent can enhance the efficiency of gangue metal separation from REE inthe aqueous phase. It is believed, moreover, without wishing to be boundby theory, the reducing agent may precipitate iron and manganesehydroxides from the PLS. In a further aspect, and without wishing to bebound by theory, filtration at an acidic pH in this step prevents theformation of aluminosilicate gels and/or emulsions. It is believed, inaddition, without wishing to be bound by a particular theory, it isbelieved that gels and emulsions can prevent downstream steps of theprocess from proceeding to completion and can interfere with pumping andmixing. In an even further aspect, an effective amount of an oxidizingagent can be added to based on the equation:H₂O₂=Df(Fe+(2Mn)),where:

-   -   H₂O₂=hydrogen peroxide (moles)    -   Df=design factor    -   Fe=total iron (moles)    -   Mn=total manganese (moles)        such that Df has a value of about 1.05 to about 1.7, about 1.1        to about 1.6, about 1.2 to about 1.5; or a sub-range within the        foregoing ranges; or a value or set of values within any of the        foregoing ranges.

In any of the above aspects, mixers in any step that requires a mixercan be connected in sequence to aid in product transfer from one mixerto the next. In some aspects, any of the above processes can beconducted partially (i.e., not to completion) if it is desired to reducecost.

In a further aspect, in step 12, as disclosed above,

In one aspect, in step 13 as disclosed above, residual solids discardedin this step can include a large portion of silicon. In a furtheraspect, step 13 removes essentially all silicon from the feedstock. In afurther aspect, a filter or other separation mechanism such as, forexample, a plate and frame filter press, can be used to separate solidsfrom liquid. In a further aspect, solids are retained in the filter orfilter press, which is then cleaned and can be re-used. In some aspects,the filtering component can be made from or lined with polypropylenecloth.

In another aspect, in step 15 as disclosed above, the desired resultantsolution pH can be from about 2.8 to about 3, or can be about 2.8, 2.85,2.9, 2.95, or about 3, or a combination of any of the foregoing values,or a range encompassing any of the foregoing values. In some aspects,when HCl is used as the acid in step 13, MgO may be a suitable base foruse in step 15. In other aspects, other bases can be used including, butnot limited to, NaOH, KOH, ammonia or ammonium hydroxide, calciumpellets, quicklime, lime slurry, or a combination thereof. In oneaspect, the base is NaOH.

In one aspect, in step 16 as disclosed herein, residual solids discardedtypically include iron. In a further aspect, step 13 removes essentiallyall iron from the feedstock. In a further aspect, a filter or otherseparation mechanism such as, for example, a filter press or a plate andframe filter press, can be used to separate solids from liquid. In afurther aspect, solids are retained in the filter or filter press, whichis then cleaned and can be re-used. In some aspects, the filteringcomponent can be made from or lined with polypropylene cloth. In someaspects, an oxidizing agent can optionally be used in step 13 to convertferrous iron to ferric iron, which, without wishing to be bound bytheory, may help with precipitation of iron compounds. In a furtheraspect, the oxidizing compound can be hydrogen peroxide or anotherchemical oxidizer. In an alternative aspect, mechanical orelectrochemical oxidation can be used.

A flow diagram of the disclosed process can be seen in FIG. 23 . Agraphical representation of the disclosed process including optionalscandium collection (step 5) can be seen in FIG. 24 . In a furtheraspect, the process described herein can be implemented in a mobile- orcommercial-scale plant described herein as follows.

FIGS. 25A-25B show a flow diagram of an exemplary process to produce aPLS as disclosed herein. The plant includes means 700 for transferringraw AMD feedstock to a separator and a means 702 for adding base toraise the resultant solution pH to from about 4 to about 4.5 as well asa means 704 for adding flocculating agents if necessary and a means 706for separating solid and aqueous phases and for discarding solids. Ifscandium recovery is performed, an optional scandium recovery device 708is incorporated at this stage. The scandium recovery device 708 includesa means 710 for transferring the aqueous phase to a separator, a means712 for adding enough base to raise the resultant solution pH to fromabout 4.5 to about 5, a means 714 to add optional flocculating and/orcoagulating agents, and a means 716 for separating solid and aqueousphases and collecting a scandium-enriched solid concentrated. Theresultant material from this step or from separation a means 706 ifscandium recovery is not performed is transferred to separator 718. Ameans 720 for adding base to the separator 718 dispenses base untilsolution pH is from about 8.0 to about 8.5, while a means 722 addsoptional flocculating and/or coagulating agents and a device 724discharged effluent for standard water treatment while collecting anREE-enriched preconcentrate for further processing. The collectedREE-enriched pre-concentrate, i.e., the HPC, is hydraulicallytransferred to a primary cone settling tank 725, and settling is allowedto proceed such that the solids collect in the lower portion of the conetank 727, and the supernatant is removed and can be further processed bystandard water treatment methods 729. The slurry in the lower portion ofthe cone tank 727 is hydraulically transferred 750 to a secondary conetank and settling allowed to proceed 752. The slurry that has collectedin the lower portion of the secondary cone tank forms a conditioned HPCthat can be transferred to a mixing tank 754. The transfer of theconditioned HPC to a mixing tank can be direct or the conditioned HPCmay be transferred to containers or vessels for transport to the mixingtank, e.g., the conditioned HPC can be transferred to suitable drums,tanker railroad car or tanker truck. After transfer to a mixing tank754, a mineral acid is added in an amount sufficient to lower the pH ofthe conditioned HPC to about 3.0 as shown at 756. Optionally, aflocculent agent may be added after acid addition 758. The solution isfiltered to remove residual solids as shown at 760, which are discarded,and the filtrate is transferred to a mixing tank 762. A base is thenadded in an amount sufficient to raise the pH of the solution to a pHabout 4.5-5.0 as shown at 764. The solution is then subject tofiltration to remove residual solids as shown at 738, which are disposedof, and the filtrate is the PLS 740. The PLS 740 can be utilizeddirectly in a solvent extraction process 742. Alternatively, the PLS 740can be stored, e.g., suitable storage tank or system. It can also bedispensed into suitable containers or vessels for transport to a sitefor solvent extraction, e.g., dispensed to drums, railroad tanker cars,or truck tanker.

FIG. 26A shows a diagram of a plant that can produce a PLS according tothe process of FIGS. 25A-25B or another exemplary process as disclosedherein. The cone tank concentrating steps described can be replaced byuse of geobags. A diagram of such a process is shown in FIG. 26B. Ageobag, e.g., a geosynthetic geobag, can be constructed of wovengeotextile materials, nonwoven textile materials, or combinationsthereof. A geobag can be used int the disclosed processes for thepurposes of storage, filtration, and drainage over a period of timesuitable for the solids in concentration to aggregate into flocs,settle, filter, and drain of aqueous effluent. The nonwoven geotextilematerials can comprise polypropylene, low- and high density polyethylenefibers extruded or sprayed into a stable and continuous network offibers having round, square, or high surface area contoured crosssections that will retain relative position under performanceapplication. Moreover, these materials exhibit low degradation whenexposed to chemical, alkali, acidic, and biological exposure. Thecharacteristics of the woven planar geotextiles are yarn or threadfibers having high tenacity monofilament or slit film which retain theirrelative position and furthermore, will exhibit low degradation whenexposed to chemical, alkali, acidic, and biological exposure.

In various aspects, as shown diagrammatically in FIGS. 26A-26B, the HPCfrom clarifier #2 can be concentrated or dewatered by at least twoalternative processes as discussed above. In a first process fordewatering, primary and secondary cone tanks can be utilized. The HPCentering the cone tank can have a solids concentration of ˜0.2% solidsafter being dosed with cationic polymer flocculant have a potentialrange of concentrations between 0.5 to 4 ppm. Following 1 hour ofgravity settling, the solids content can reach ˜1% solids. Thesupernatant water is decanted, and the solids are transferred to asecond cone tank (secondary cone tank). This slurry can settle forapproximately 1 hour and following the solids settling, the supernatantis removed and the resulting solids content is approximately 1.4%.

Alternatively, a second process for dewatering comprises use of geobags.The HPC from the clarifier #2 can be transferred to a group of geobagsand water allowed to drain. The geobags are designed to retain the HPCin the geobag and allow the HPC particulates to filter. The decant watercan drain through the bag. The bags can be maximized in length and girthand be fitted in the given laydown area. The HPC filtration anddewatering process can use multiples of two geobags that may be filledsingularly in series, in parallel, or by alternating between the twobags. This filling process maximizes HPC solids generation to the rateof solids' filtration and dewatering. The decanted and filtered watercan be collected and discharged in compliance with the permittedenvironmental discharge limits. The HPC can remain in the geobag untilthe proper percent solids is obtained. When the proper percent solidsare acceptable, the geobag(s) can be cut open and the dewatered HPCmaterial can be removed and transported to the PLS mixing vessel. Thegeobag material can be removed for off-site disposal, and new geobag(s)can be installed to repeat the process. The process cycles with fillingthe bags, allowing them to decant until a desired percentage of solidsis obtained, followed by material removal and new bag placement. Thebags can be designed to allow for maximum vertical storage and allow fordrying in a reasonable amount of time. It was determined in exemplarystudies that based on a 200 gallon per minute inflow of HPC with 0.05 to0.3% solids content, the HPC can be dewatered to a targeted averageTotal Solids of 4.0 to 6.0% between initial fills. Potential increasesin Total Solids up to 90% may be achieved depending on controlling theHPC flocculation process and environmental exposure conditions (heat,humidity, wind, rain).

The geobag specifications of the woven type can range in ApparentOpening Size (AOS) between 0.25 to 0.50 mm, and for nonwoven type theAOS range can be about 0.10 to 0.20 mm as measured according to ASTMD4751. Geobags can be configured as geocomposite multi-layered planarsurfaces of an outer woven layer to develop radial tensile strength,coupled with an internal nonwoven layer to develop low permittivity andlow AOS. The functional performance range of the outer woven layerfunctions in grab tensile strength ranging 300-400 N and at anelongation strain of 12-17% (as determined according to ASTM D4632). Theinner non-woven layer performance range for filtration and drainageexhibits the AOS range is about 0.10 to 0.32 mm as measured to ASTMD4751 and a permittivity ranging from about 0.75 to 0.95 sec-1 (asdetermined according to ASTM D4491).

Suitable commercially available geobag products include, but are notlimited to, Tencate (Mirafi®) brand for woven fabrics include the FW300, 402, 403, 404, and 700 products; and for nonwoven fabrics include140N, 170N, and 1100N products.

Upstream Concentrator.

Full-Scale Unit Construction. In one aspect, disclosed herein is afull-scale AMD treatment plant with an integrated REE/CM recoveryoperation. In a further aspect, potential alterations to the treatmentplant can include, but are not limited to: (1) staged precipitationusing multiple clarifiers/thickeners in series; (2) independent pHcontrol in each clarifier; and (3) additional materials handling andfiltration units to recover and dewater the REE-enriched concentrates.

In a further aspect, to augment the traditional AMD treatment system, astate-of-the-art automation and control system to remotely monitor keyoperating parameters is disclosed herein. In another aspect, thispackage can provide real-time measurements of pump and mixer motorconditions, pH measurements, select ion concentrations, and othervariables. In still another aspect, these values can be logged in anarchival data format and used for feedback loop control.

In one aspect, all parts of the process disclosed herein can beconducted while following all pertinent local, state, and federalregulations. In another aspect, upon completion of the constructionactivities a safety analysis/review can be performed prior to equipmentstartup and shakedown.

Full-Scale Unit Operation. In one aspect, disclosed herein are thefollowing parameters for full-scale operation of an upstreamconcentrator as disclosed herein: (1) the specific locations of samplingpoints within the system and expected consistency of those samples(liquid, solid, or slurry); (2) the specific procedures for obtaining,handling, transporting, and storing various sample types; (3) theexpected frequency and extent of sample collection for both routine andintensive analysis; (4) the specific protocols for analyzing samples andinterpreting the resultant data; and (5) the protocols for retaining andarchiving samples.

In one aspect, disclosed herein is a test matrix to gather performancedata under different operating conditions while ensuring that the finalwater discharge meets National Pollutant Discharge Elimination System(NPDES) permit requirements. In a further aspect, the test matrix isbased on results from the small-scale unit evaluation and includesexpected variations in AMD flow and REE concentration that followseasonal variations throughout the calendar year. In a further aspect,these natural variations can be tracked over time and used to evaluatethe robustness and resiliency of the REE/CM enrichment process.

In a further aspect, after identifying and validating the optimalprocess operational parameters, the upstream concentrator will beoperated continuously at those settings. In one aspect, REE/CMpreconcentrates generated during this time will be collected into55-gallon drums or geotextile super sacks and stored for future testingin the disclosed downstream processing units.

Acid Leaching/Solvent Extraction.

System Design. In one aspect, disclosed herein is a system thatprocesses the preconcentrates generated from the large-scale upstreamconcentration unit, e.g., from PLS or HPC as disclosed herein. Furtherin this aspect, the system includes, but is not limited to: (1) amass-balanced process flowsheet, (2) piping and instrumentationdiagrams, (3) a proposed facility layout, (4) a construction costestimate based on vendor quotes, (5) a daily operational cost estimate,and (6) final engineering drawings of the pilot-scale plant.

In one aspect, the pilot-scale facility is co-located with the upstreamconcentrator at the host site. Further in this aspect, this location hasadequate access to water, power, and other utilities that will berequired for the pilot-scale system. In still another aspect, onlyminimal changes to the facility will be required prior to systemcommissioning.

System Procurement, Construction, and Installation. In one aspect, sitepreparation may include clearing unnecessary equipment, reinforcingfoundations or structures, and/or adding mechanical and electricalutilities. In a further aspect, these initial preparations ensure thatequipment installation and assembly can be completed in a timely manner.In a still further aspect, fabricated components and final equipment canbe shipped directly to the host site.

System Shakedown, Training, and Troubleshooting. In one aspect, theprimary safety hazard expected herein is the use of strong acids in theleaching and solvent extraction units. At a minimum, acid resistantgloves and gowns and adequate ventilation in the testing area can beused to minimize risk to personnel, as will laboratory safety andchemical hygiene training.

In one aspect, a series of shakedown tests will be conducted to identifyand resolve operational issues that may arise during the detailed systemtesting. In a further aspect, shakedown testing can provide anopportunity to mitigate these issues while providing key operationaldata that can support a detailed test campaign. In a still furtheraspect, specific goals of this testing program include, but are notlimited to: (1) verify vendor specifications on capacity and power; (2)ensure the sufficiency of various ancillary equipment and utilities; (3)identify the operational limits to be used in detailed system testing.In a still further aspect, shakedown testing can be conducted byoperating all unit operations under “water-only” conditions to firstensure the structural integrity of the process units. Further in thisaspect, after water-only testing, solids can be slowly incorporated intothe test regimen to ensure the adequacy of valves, pumps, and otherfittings. In another aspect, strong acids and other chemicals can beadded only after the system has been proven in these more benignconditions.

In one aspect, disclosed herein is a state-of-art real time monitoringand control system that can provide real-time measurements of pump andmixer motor conditions, pH measurements, select ion concentrations, andother variables. In a further aspect, these values can be logged in anarchival data format and used for feedback loop control. In stillanother aspect, this task also includes all troubleshooting needed toensure consistent and safe operation of the pilot-scale system.

System Parametric Testing. In one aspect, using feedstocks produced fromprevious stages of the process disclosed herein, acid leaching andsolvent extraction tests can be conducted over an extended operatingperiod. In another aspect, each experimental condition may require atleast 64 hours of continuous testing, and the solvent extraction (SX)operation is anticipated to run continuously for 24 hours per day. Instill another aspect, the specific items to be analyzed during this testcampaign may include but are not limited to: (1) the influence of SXextractant type and concentration; (2) the influence of SX solvent typeand ratio; (3) the influence of extracting and stripping acid type andpH; (4) the number of extracting and stripping stages needed to reachthe target purity level. In another aspect, provided herein are pathwaysto remove non-target impurities and optimize the process with regards toseparation efficiency, solvent recycling, and waste minimization. In oneaspect, a test matrix can be generated using a statistical design ofexperiments, and specific conditions can be blocked and repeated toassess experimental error while mitigating the influence of covariates,such as ambient environmental conditions. In yet another aspect, resultsfrom this experimental design can be analyzed using a response surfacemethodology to identify the optimal conditions leading to the highestrecovery and selectivity.

Alternative Feedstock Testing.

In one aspect, after meeting objectives using the preferred AMDfeedstock, other feedstocks can be evaluated in the ALSX pilot plant. Ina further aspect, specific examples include, but are not limited to, AMDtreatment sludges, coal refuse and under clays, fly ash and gasificationchar, other REE-enriched coal byproducts, and combinations thereof.

Laboratory Support and Testing.

In one aspect, both aqueous and solid samples can be routinely analyzedfor REE/CM, major gangue metals, trace gangue metals, and CMs. In afurther aspect, REE aqueous concentrations can be determined usinginductively coupled plasma-mass spectrometry (ICP-MS). In a stillfurther aspect, solid samples can be digested by sodium peroxide (Na₂O₂)fusion and re-dissolution in hydrochloric acid and resulting aqueousanalysis can then be undertaken using ICP-MS. In one aspect, major ionssuch as iron (Fe) and aluminum (Al) will be determined by a suitabletechnique such as, for example, inductively coupled plasma opticalemission spectrometry (ICP-OES).

In yet another aspect, a broad scan of feedstocks can be used toidentify other CMs and, if economically attractive, ensure that thedisclosed ALSX process is modified for their recovery.

Economic Systems Analysis.

In one aspect, experimental results from the various testing campaignsas well as model results from the system design optimization can becompiled into a techno-economic analysis (TEA). Further in this aspect,the analysis can report costs and performance at the existing scale andproject those costs to the next design scale and/or a commercialimplementation using standard scaling factors and itemized costs asappropriate. In one aspect, all analyses will use guidelines andassumptions provided by the National Energy Technology Laboratory(NETL), and results will be presented in accordance with NI 43-101reporting standards for disclosing mineral projects. In any of theseaspects, at a minimum, this analysis will include: a clear statement ofthe assumptions; cash forecasts on an annual basis; a discussion ofpotential net present value (NPV) and internal rate of return (IRR); asummary of the tax structure imposed; and a sensitivity analysis withrespect to grade, price, and other significant input factors.

In one aspect, an environmental systems analysis can be conductedconcurrently with the other project activities and may focus on twospecific objectives: materials handling considerations and environmentalcompliance. In one aspect, the materials handling design will addressthe dewatering, filtration, and the short- and long-term materialstorage requirements for the upstream concentration process. In oneaspect, specific research tasks to be addressed for the materialhandling system design include, but are not limited to:

-   -   1. In one aspect, the following elements for the woven        geotextile GEOTUBE® bags proposed for the first and second        splits have been explored at field scale: engineering strength        and permittivity design, GEOTUBE® proportion sizing (length and        diameter ratios), GEOTUBE® stacking configurations and        techniques to ensure safe and environmentally benign dewatering        operations.    -   2. In another aspect process treatment requirements for the        GEOTUBE® water filtrate, primary liquid containment, liquid        transport design and layout, and geotechnical material        characterization consisting of material testing for physical,        strength and permeability properties will be determined.    -   3. In another aspect, a series of numerical modeling activities        can be performed for mathematical characterization of drainage        in the system and the potential improvements. The outcome of the        modeling is to compare and contrast with the laboratory testing        and field results.    -   4. In still another aspect, increasing process efficiency can be        studied to identify and reduce barriers to future technology        entry into the REE/CM commercialization. Further in this aspect,        one specific area for efficiency improvement is sediment        dewatering of the feedstock from splits 2 and 3, and the        iron-rich sediment from split 1.

In one aspect, using hydrometallurgical methods in the disclosed processat the bench scale, a concentrate with 80% rare earth oxides wasproduced from AMD treatment sludge (FIG. 9 ).

In one aspect, extraction of REE/CM from AMD treatment precipitates andfrom untreated AMD was evaluated. In one aspect, unprocessed AMDtreatment solids can be transported to a central ALSX facility for finalprocessing into a high grade MREO. In an alternative aspect, a fieldconcentrate can be extracted and dewatered upstream of a conventionalAMD treatment plant and transported to the ALSX facility. In a furtheraspect, the process disclosed herein can accept and produce an REE/CMconcentrate from either source.

HPC Composition.

In various aspects, the present disclosure pertains to a HPC compositionobtained from an input source, e.g., an AMD feedstock material, usingthe disclosed processes, methods, and systems. In a further aspect, thedisclosed HPC composition is enriched in one or more REE materialcompared to the AMD feedstock material used. The disclosed HPScomposition can be used in further steps, as disclosed herein, tofurther enrich or purify one or more REE material, e.g., as a feedstockmaterial for production of a disclosed PLS composition.

PLS Composition.

In various aspects, the present disclosure pertains to a PLS compositionobtained from an input source, e.g., a HPC composition, using thedisclosed processes, methods, and systems. In a further aspect, thedisclosed PLS composition is enriched in one or more REE materialcompared to the HPC composition used. The disclosed PLS composition canbe used in further steps, as disclosed herein, to further enrich orpurify one or more REE material.

AMD may occur from coal and hard rock mining activities and the like. Atreatment location site may include but is not limited to hard rockmines, backfilled coal mining waste, backfilled mining waste, waste rockpiles, copper mines, gold mines, lead mines, silver mines, coal mines,and the like. In various aspects, the AMD used in the disclosed methodsand composition include at least one acid mine drainage generationsource. An acid mine drainage generation source may be identified at atreatment location site with an acid mine drainage generation sourceidentifier. Identification may include human evaluation, site surveymethods, electromagnetic induction surveys, ground electromagneticinduction surveys, air electromagnetic surveys, and the like.

The least one acid mine drainage generation source providing AMDfeedstock material may be derived from, associated with, or originatewith various coal and hard rock mining activities and the like. Atreatment location site may include but is not limited to hard rockmines, backfilled coal mining waste, backfilled mining waste, waste rockpiles, copper mines, gold mines, lead mines, silver mines, coal mines,and the like. In embodiments, a treatment location site may include atleast one acid mine drainage generation source. An acid mine drainagegeneration source may be identified at a treatment location site with anacid mine drainage generation source identifier. Identification mayinclude human evaluation, site survey methods, electromagnetic inductionsurveys, ground electromagnetic induction surveys, air electromagneticsurveys, and the like. Utilization of electromagnetic induction surveys,sometimes referred to as EM mapping, may determine areas of lowresistance in a treatment location site and may even measure changes insubsurface resistivity throughout a site. Low resistance may be anindication of acid mine drainage generation source material.Accordingly, EM mapping may provide valuable information in potentialhotspots and perhaps even acid mine drainage plume movement within asite. From an identification of an acid mine drainage generation source,at least one treatment area may be determined as optimal foradministering a treatment injection. As such, at least one injectionwell may be installed in the treatment areas.

In a further aspect, the PLS composition can vary depending on thecomposition of the AMD feedstock used. Representative average valuesthat were experimentally determined for multiple PLS compositionsprepared using the disclosed processes, methods, and devices are shownin Tables 1 below.

TABLE 1 Distribution of Elemental Concentrations from Typical PLSSamples. Number of Standard Confidence Element Samples Mean* Median*Min.* Max.* Deviation* Interval* Al 33 4701.78 2736.24 2130.78 21,446.324637.25 1644.30 Ca 33 1008.67 745.22 590.10 2605.74 537.24 190.50 Co 3343.56 24.04 18.43 195.29 46.09 16.34 Fe 33 363.78 4.96 2.20 3823.39961.16 340.81 Mg 33 3068.26 2353.81 164.19 13,134.87 3109.94 1102.74 Mn33 987.22 707.77 74.44 3689.29 963.37 341.60 Na 33 9225.59 9619.27 47.5528,475.75 6479.95 2297.69 Ni 17 56.25 49.94 38.63 91.94 16.24 8.35 Si 33346.34 73.96 32.54 3559.26 783.14 277.69 Zn 17 242.70 110.26 85.24686.61 222.97 114.64 SO₄ 33 1059.86 1011.56 25.39 3141.38 518.79 183.96Cl 33 9.38 5.06 2.04 77.87 12.86 4.56 Sc 31 552.50 133.92 74.75 2822.18785.28 288.04 Y 33 23,970.81 13,527.36 7151.53 111,224.38 24,997.978863.89 La 33 6221.13 2697.71 1477.79 32,650.27 7826.85 2775.28 Ce 3316,906.87 7749.36 4906.65 86,414.33 20,395.50 7231.93 Pr 33 2405.261281.05 782.96 10,803.77 2498.28 885.85 Nd 33 11,344.41 6492.20 3688.0748,145.36 10,774.42 3820.44 Sm 33 3178.51 2087.37 1133.53 12,001.322548.86 903.78 Eu 33 838.37 530.82 302.10 3,223.56 688.45 244.12 Gd 334850.06 3046.42 1820.15 18,229.43 3932.68 1394.47 Tb 33 789.93 484.26339.07 3,021.65 660.37 234.16 Dy 33 4491.55 2574.64 1995.76 18,229.214100.69 1454.04 Ho 33 885.34 487.86 354.92 3639.79 830.31 294.41 Er 332317.29 1227.86 908.26 10,032.59 2302.52 816.44 Tm 33 296.40 151.07112.90 1291.24 298.81 105.95 Yb 33 1645.19 827.17 638.35 7380.85 1707.64605.50 Lu 33 242.53 123.16 91.79 1100.99 251.70 89.25 Th 25 37.28 6.140.06 322.19 75.65 31.23 U 33 359.75 267.88 198.47 1205.17 219.05 77.67*Units for aluminum through chloride are mg/L. Units for scandiumthrough uranium are μg/L.

Further representative average values that were experimentallydetermined for multiple PLS compositions prepared using the disclosedprocesses, methods, and devices are shown in Table 2 below.

TABLE 2 Typical PLS Composition. aqueous % 20′0852 mg/L TREE Sc 0.3 1.3%Y 5.7 24.5%  La 1.5 6.3% Ce 3.8 16.2%  Pr 0.7 3.1% Nd 2.9 12.6%  Sm 1.35.5% Eu 0.3 1.4% Gd 1.9 8.3% Tb 0.4 1.6% Dy 1.9 8.0% Ho 0.4 1.7% Er 1.04.3% Tm 0.2 0.7% Yb 0.9 3.9% Lu 0.1 0.6% TREE 23.3 Co 17.9  77% TREE +Co 41.2 Th + U 0.4 1.8% mg/L Gangue Al 2,625.7 Fe 10.2 Mn 84.6 Ni 41.2Si 25.7 Zn 126.6 2,913.9 other ions Ca 1,546.0 Mg 528.6 Na 27,548.2 SO40.0 Cl 5.4 29,628.2

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least three of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least four of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least five of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least six of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least seven of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least eight of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least nine of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises at least ten of lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of at least about 10 mg/L, about 11 mg/L, about 12 mg/L,about 13 mg/L, about 14 mg/L, about 15 mg/L, about 16 mg/L, about 17mg/L, about 18 mg/L, about 19 mg/L, about 20 mg/L, about 21 mg/L, about22 mg/L, about 23 mg/L, about 24 mg/L, about 25 mg/L, about 26 mg/L,about 27 mg/L, about 28 mg/L, about 29 mg/L, about 30 mg/L, about 31mg/L, about 32 mg/L, about 33 mg/L, about 34 mg/L, about 35 mg/L, about36 mg/L, about 37 mg/L, about 38 mg/L, about 39 mg/L, about 40 mg/L,about 41 mg/L, about 42 mg/L, about 43 mg/L, about 44 mg/L, about 45mg/L, about 46 mg/L, about 47 mg/L, about 48 mg/L, about 49 mg/L, about50 mg/L; or a range encompassed by any two of the foregoing values; orany set of the foregoing values; wherein it is understood that the TREEcomprises lanthanum, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises three or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least three oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least four oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least five oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least six oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least seven oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least eight oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least nine oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises at least ten oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium.

In a further aspect, the PLS composition comprises TREE present at aconcentration of about 5 mg/L to 100 mg/L, 5 mg/L to 95 mg/L, 5 mg/L to85 mg/L, 5 mg/L to 80 mg/L, 5 mg/L to 75 mg/L, 5 mg/L to 70 mg/L, 5 mg/Lto 65 mg/L, 5 mg/L to 60 mg/L, 5 mg/L to 55 mg/L, 5 mg/L to 50 mg/L, 5mg/L to 45 mg/L, 5 mg/L to 40 mg/L; or a sub-range within any of theforegoing ranges; or any set of the values with the foregoing ranges;wherein it is understood that the TREE comprises lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium,scandium, and yttrium.

In a further aspect, the PLS composition comprises four or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises fiver or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises six or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises seven or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises eight or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises nine or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises ten or more of thefollowing materials in the indicated amounts: Sc present at aconcentration of from about 0.05 mg/L to about 1 mg/L; Y present at aconcentration of from about 0.5 mg/L to about 10 mg/L; La present at aconcentration of from about 0.05 mg/L to about 5 mg/L; Ce present at aconcentration of from about 0.5 mg/L to about 7.5 mg/L; Pr present at aconcentration of from about 0.05 mg/L to about 2.5 mg/L; Nd present at aconcentration of from about 0.5 mg/L to about 10 mg/L; Sm present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; Eu present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Gd present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tb present at aconcentration of from about 0.05 mg/L to about 1.5 mg/L; Dy present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Ho present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Er present at aconcentration of from about 0.1 mg/L to about 5 mg/L; Tm present at aconcentration of from about 0.05 mg/L to about 2 mg/L; Yb present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and Lu present ata concentration of from about 0.01 mg/L to about 1 mg/L; or a sub-rangewithin any of the foregoing ranges; or one or more discrete valueswithin any of the foregoing ranges.

In a further aspect, the PLS composition comprises the followingmaterials in the indicated amounts: Sc present at a concentration offrom about 0.05 mg/L to about 1 mg/L; Y present at a concentration offrom about 0.5 mg/L to about 10 mg/L; La present at a concentration offrom about 0.05 mg/L to about 5 mg/L; Ce present at a concentration offrom about 0.5 mg/L to about 7.5 mg/L; Pr present at a concentration offrom about 0.05 mg/L to about 2.5 mg/L; Nd present at a concentration offrom about 0.5 mg/L to about 10 mg/L; Sm present at a concentration offrom about 0.1 mg/L to about 2.5 mg/L; Eu present at a concentration offrom about 0.05 mg/L to about 1.5 mg/L; Gd present at a concentration offrom about 0.1 mg/L to about 5 mg/L; Tb present at a concentration offrom about 0.05 mg/L to about 1.5 mg/L; Dy present at a concentration offrom about 0.1 mg/L to about 5 mg/L; Ho present at a concentration offrom about 0.05 mg/L to about 2 mg/L; Er present at a concentration offrom about 0.1 mg/L to about 5 mg/L; Tm present at a concentration offrom about 0.05 mg/L to about 2 mg/L; Yb present at a concentration offrom about 0.05 mg/L to about 5 mg/L; and Lu present at a concentrationof from about 0.01 mg/L to about 1 mg/L; or a sub-range within any ofthe foregoing ranges; or one or more discrete values within any of theforegoing ranges.

In a further aspect, the disclosed PLS composition comprises Fe a lowerconcentration than present in the AMD feedstock. In a still furtheraspect, the disclosed PLS composition comprises Fe at a concentrationless than about 25 mg/L, about 24 mg/L, about 23 mg/L, about 20 mg/L,about 19 mg/L, about 18 mg/L, about 17 mg/L, about 16 mg/L, about 15mg/L, about 14 mg/L, about 13 mg/L, about 12 mg/L, about 10 mg/L, about9 mg/L, about 8 mg/L, about 7 mg/L, about 6 mg/L, about 5 mg/L; or arange having a lower limit of essentially about 0 mg/L to an upper limitthat is any of the foregoing values; or a range having a lower limit ofessentially about 5 mg/L to an upper limit that is any of the foregoingvalues; or a range having a lower limit of essentially about 7.5 mg/L toan upper limit that is any of the foregoing values; or any combinationof the foregoing values.

In a further aspect, the disclosed PLS composition comprises thorium anduranium present in a total concentration of less than about 10 mg/L,about 9 mg/L, about 8 mg/L, about 7 mg/L, about 6 mg/L, about 5 mg/L,about 4 mg/L, about 3 mg/L, about 2 mg/L, about 1 mg/L, about 0.9 mg/L,about 0.8 mg/L, about 0.7 mg/L, about 0.6 mg/L, about 0.5 mg/L, about0.4 mg/L, about 0.3 mg/L, about 0.2 mg/L, about 0.1 mg/L; or a rangeencompassed by any two of the foregoing values; or any set of theforegoing values.

In a further aspect, the disclosed PLS composition comprises cobalt inan amount of about 1 mg/L to about 30 mg/L, about 1 mg/L to about 25mg/L, about 1 mg/L to about 20 mg/L, about 1 mg/L to about 15 mg/L,about 5 mg/L to about 30 mg/L, about 5 mg/L to about 25 mg/L, about 5mg/L to about 20 mg/L, about 5 mg/L to about 15 mg/L, about 10 mg/L toabout 30 mg/L, about 10 mg/L to about 25 mg/L, about 10 mg/L to about 20mg/L, about 10 mg/L to about 15 mg/L, about 15 mg/L to about 30 mg/L,about 15 mg/L to about 25 mg/L, about 15 mg/L to about 20 mg/L, about 20mg/L to about 30 mg/L, about 20 mg/L to about 25 mg/L; or a sub-rangewithin any of the foregoing ranges; or a set of values within any of theforegoing ranges.

In a further aspect, the disclosed PLS composition comprises about 50 wt% to about 80 wt % cobalt, about 55 wt % to about 80 wt % cobalt, about60 wt % to about 80 wt % cobalt, about 65 wt % to about 80 wt % cobalt,about 70 wt % to about 80 wt % cobalt, about 50 wt % to about 85 wt %cobalt, about 55 wt % to about 85 wt % cobalt, about 60 wt % to about 85wt % cobalt, about 65 wt % to about 85 wt % cobalt, about 70 wt % toabout 85 wt % cobalt, about 50 wt % to about 90 wt % cobalt, about 55 wt% to about 90 wt % cobalt, about 60 wt % to about 90 wt % cobalt, about65 wt % to about 90 wt % cobalt, about 70 wt % to about 90 wt % cobalt;or any sub-range within the foregoing ranges; or any set of valueswithin the foregoing ranges.

REFERENCES

The following references are cited herein throughout.

-   -   Ref 1. Stumm, W., and Morgan, J. J. 1995. Aquatic Chemistry,        Chemical Equilibria and Rates in Natural Waters, 3rd ed.        Hoboken, NJ: John Wiley & Sons, Inc.: 1022 pp.    -   Ref 2. Kim, E and Osseo-Asare, K. 2012. “Aqueous stability of        thorium and rare earth metals in monazite hydrometallurgy: Eh-pH        diagrams for the systems Th—, Ce—, La—, Nd—(PO4)-(SO4)-H2O at        25° C.,” Hydrometallurgy, 113-114:67-78.    -   Ref 3. Pourbaix, M., 1966. Atlas of electrochemical equilibrium        in aqueous solution. New York, NY: Pergamon.    -   Ref 4. Bourricaudy, Ernesto et al. 2016. “Commissioning of a        Mini SX Pilot Plant at SGS Minerals—Lakefield Site”. In: IMPC        2016: XXVIII International Mineral Processing Congress        Proceedings. Quebec, Canada: pp. 1-16.    -   Ref 5. Chiarizia, Renato and Alexandra Briand, 2007. “Third        phase formation in the extraction of inorganic acids by TBP in        n-Octane,” Solvent Extraction and Ion Exchange, 25:351-371.    -   Ref 6. Kedari, C S et al., 2006. “Third Phase Formation in the        Solvent Extraction System Ir (IV)— Cyanex 923,” Solvent        Extraction and Ion Exchange, 23:545-559.    -   Ref 7. Koermer, Scott and Aaron Noble (2018). “Unpublished        Solvent Extraction Research”. PhD thesis. Virginia Polytechnic        University.    -   Ref 8. Ren, Panpan, 2019. “Recovery of Rare Earth Elements        (REEs) from Coal Mine Drainage Sludge Leachate,” PhD thesis.        West Virginia University.    -   Ref 9. Ritcey, G. M., 1980. “Crud in solvent extraction        processing—a review of causes and treatment,” Hydrometallurgy,        5:97-107.    -   Ref 10. Ritcey, G. M. and A. W. Ashbrook, 1979. Solvent        Extraction Principles and Applications to Process Metallurgy        Part II. Volume 1. Amsterdam: Elsevier Scientific Publishing.    -   Ref 11. Ritcey, G. M. and A. W. Ashbrook, 1984. Solvent        extraction Principles and Applications to Process Metallurgy        Part I. Volume 1. Amsterdam: Elsevier Scientific Publishing.    -   Ref 12. Takeno, Naoto, 2005. “Atlas of Eh-pH        diagrams—Intercomparison of thermodynamic databases” Geological        Survey of Japan, Tech. Rep. 419:1-287.    -   Ref 13. Wang, Weiwei, Yoko Pranolo, and Chu Yong Cheng, 2013.        “Recovery of scandium from synthetic red mud leach solutions by        solvent extraction with D2EHPA,” Separation and Purification        Technology, 108: 96-102.        Aspects.

The following listing of exemplary aspects supports and is supported bythe disclosure provided herein.

Aspect 1. A method for preparing a HPC enriched in rare earth elementsand critical minerals, the method comprising: (a) contacting a rawmaterial with a first base in an amount sufficient to adjust the pH to avalue from about 4.0 to about 6.0, thereby forming a mixture comprisinga first aqueous phase and a first solid concentrate; (b) separating thefirst aqueous phase from the first solid concentrate; (c) contacting thefirst aqueous phase with a second base in an amount sufficient to adjustthe pH to a value from about 7.0 to about 9.0, thereby forming a mixturecomprising a second aqueous phase and the hydraulic pre-concentrate; (d)removing the second aqueous phase and collecting the hydraulicpre-concentrate; wherein the raw material comprises rare earth elements;and wherein the hydraulic pre-concentrate is enriched in rare earthelements; and optionally wherein the first solid concentrate is enrichedin Sc compared to the raw material.

Aspect 2. The method of Aspect 1, wherein the raw material comprises rawacid mine drainage (AMD), an AMD precipitate (AMDp), an enriched AMDprecipitate (eAMDp), or combinations thereof.

Aspect 3. The method of Aspect 2, wherein the raw material comprises rawacid mine drainage (AMD).

Aspect 4. The method of any one of Aspect 1-Aspect 3, wherein the rawmaterial has a pH less than about 4.0.

Aspect 5. The method of Aspect 4, wherein the raw material has a pH offrom about 0.1 to about 4.0.

Aspect 6. The method of Aspect 4, wherein the raw material has a pH offrom about 0.5 to about 4.0.

Aspect 7. The method of Aspect 4, wherein the raw material has a pH offrom about 0.6 to about 4.0.

Aspect 8. The method of Aspect 4, wherein the raw material has a pH offrom about 0.7 to about 4.0.

Aspect 9. The method of Aspect 4, wherein the raw material has a pH offrom about 0.8 to about 4.0.

Aspect 10. The method of Aspect 4, wherein the raw material has a pH offrom about 0.9 to about 4.0.

Aspect 11. The method of Aspect 4, wherein the raw material has a pH offrom about 1.0 to about 4.0.

Aspect 12. The method of Aspect 4, wherein the raw material has a pH offrom about 0.1 to about 3.5.

Aspect 13. The method of Aspect 4, wherein the raw material has a pH offrom about 0.5 to about 3.5.

Aspect 14. The method of Aspect 4, wherein the raw material has a pH offrom about 0.6 to about 3.5.

Aspect 15. The method of Aspect 4, wherein the raw material has a pH offrom about 0.7 to about 3.5.

Aspect 16. The method of Aspect 4, wherein the raw material has a pH offrom about 0.8 to about 3.5.

Aspect 17. The method of Aspect 4, wherein the raw material has a pH offrom about 0.9 to about 3.5.

Aspect 18. The method of Aspect 4, wherein the raw material has a pH offrom about 1.0 to about 3.5.

Aspect 19. The method of Aspect 4, wherein the raw material has a pH offrom about 0.1 to about 3.0.

Aspect 20. The method of Aspect 4, wherein the raw material has a pH offrom about 0.5 to about 3.0.

Aspect 21. The method of Aspect 4, wherein the raw material has a pH offrom about 0.6 to about 3.0.

Aspect 22. The method of Aspect 4, wherein the raw material has a pH offrom about 0.7 to about 3.0.

Aspect 23. The method of Aspect 4, wherein the raw material has a pH offrom about 0.8 to about 3.0.

Aspect 24. The method of Aspect 4, wherein the raw material has a pH offrom about 0.9 to about 3.0.

Aspect 25. The method of Aspect 4, wherein the raw material has a pH offrom about 1.0 to about 3.0.

Aspect 26. The method of Aspect 4, wherein the raw material has a pH offrom about 0.1 to about 2.5.

Aspect 27. The method of Aspect 4, wherein the raw material has a pH offrom about 0.5 to about 2.5.

Aspect 28. The method of Aspect 4, wherein the raw material has a pH offrom about 0.6 to about 2.5.

Aspect 29. The method of Aspect 4, wherein the raw material has a pH offrom about 0.7 to about 2.5.

Aspect 30. The method of Aspect 4, wherein the raw material has a pH offrom about 0.8 to about 2.5.

Aspect 31. The method of Aspect 4, wherein the raw material has a pH offrom about 0.9 to about 2.5.

Aspect 32. The method of Aspect 4, wherein the raw material has a pH offrom about 1.0 to about 2.5.

Aspect 33. The method of Aspect 4, wherein the raw material has a pH offrom about 0.1 to about 2.0.

Aspect 34. The method of Aspect 4, wherein the raw material has a pH offrom about 0.5 to about 2.0.

Aspect 35. The method of Aspect 4, wherein the raw material has a pH offrom about 0.6 to about 2.0.

Aspect 36. The method of Aspect 4, wherein the raw material has a pH offrom about 0.7 to about 2.0.

Aspect 37. The method of Aspect 4, wherein the raw material has a pH offrom about 0.8 to about 2.0.

Aspect 38. The method of Aspect 4, wherein the raw material has a pH offrom about 0.9 to about 2.0.

Aspect 39. The method of Aspect 4, wherein the raw material has a pH offrom about 1.0 to about 3.0.

Aspect 40. The method of any one of Aspect 1-Aspect 39, wherein thefirst base comprises a base selected from ammonium hydroxide, sodiumhydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide,ammonium carbonate, sodium carbonate, potassium carbonate, calciumcarbonate, magnesium carbonate, and a combination thereof.

Aspect 41. The method of Aspect 40, wherein the first base comprisescalcium hydroxide.

Aspect 42. The method of any one of Aspect 1-Aspect 39, wherein thecontacting the raw material with the first base is in an amountsufficient to adjust the pH to a value from about 4.0 to about 5.0.

Aspect 43. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.9.

Aspect 44. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.8.

Aspect 45. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.7.

Aspect 46. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.6.

Aspect 47. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.5.

Aspect 48. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.4.

Aspect 49. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.3.

Aspect 50. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.2.

Aspect 51. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.1.

Aspect 52. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 5.0.

Aspect 53. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.9.

Aspect 54. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.8.

Aspect 55. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.7.

Aspect 56. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.6.

Aspect 57. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.5.

Aspect 58. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.4.

Aspect 59. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.3.

Aspect 60. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.2.

Aspect 61. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 5.0.

Aspect 62. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.9.

Aspect 63. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.8.

Aspect 64. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.7.

Aspect 65. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.6.

Aspect 66. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.5.

Aspect 67. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.4.

Aspect 68. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.2 to about 4.3.

Aspect 69. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 5.0.

Aspect 70. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 4.9.

Aspect 71. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 4.8.

Aspect 72. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 4.7.

Aspect 73. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 4.6.

Aspect 74. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 4.5.

Aspect 75. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.3 to about 4.4.

Aspect 76. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.4 to about 5.0.

Aspect 77. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.4 to about 4.9.

Aspect 78. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.4 to about 4.8.

Aspect 79. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.4 to about 4.7.

Aspect 80. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.4 to about 4.6.

Aspect 81. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.4 to about 4.5.

Aspect 82. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.5 to about 5.0.

Aspect 83. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.5 to about 4.9.

Aspect 84. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.5 to about 4.8.

Aspect 85. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.5 to about 4.7.

Aspect 86. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.5 to about 4.6.

Aspect 87. The method of Aspect 42, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.1 to about 4.2.

Aspect 88. The method of any one of Aspect 1-Aspect 39, wherein thecontacting the raw material with the first base is in an amountsufficient to adjust the pH to a value from about 3.5 to about 4.5.

Aspect 89. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.6 to about 4.5.

Aspect 90. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 3.7 to about 4.5.

Aspect 91. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 3.8 to about 4.5.

Aspect 92. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 3.9 to about 4.5.

Aspect 93. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 4.0 to about 4.5.

Aspect 94. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 3.5 to about 4.4.

Aspect 95. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 3.6 to about 4.4.

Aspect 96. The method of Aspect 88, wherein wherein the contacting theraw material with the first base is in an amount sufficient to adjustthe pH to a value from about 3.7 to about 4.4.

Aspect 97. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.8 to about 4.4.

Aspect 98. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.9 to about 4.4.

Aspect 99. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.4.

Aspect 100. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.5 to about 4.3.

Aspect 101. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.6 to about 4.3.

Aspect 102. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.7 to about 4.3.

Aspect 103. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.8 to about 4.3.

Aspect 104. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.9 to about 4.3.

Aspect 105. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.3.

Aspect 106. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.5 to about 4.2.

Aspect 107. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.6 to about 4.2.

Aspect 108. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.7 to about 4.2.

Aspect 109. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.8 to about 4.2.

Aspect 110. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.9 to about 4.2.

Aspect 111. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.2.

Aspect 112. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.5 to about 4.1.

Aspect 113. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.6 to about 4.1.

Aspect 114. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.7 to about 4.1.

Aspect 115. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.8 to about 4.1.

Aspect 116. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 3.9 to about 4.1.

Aspect 117. The method of Aspect 88, wherein the contacting the rawmaterial with the first base is in an amount sufficient to adjust the pHto a value from about 4.0 to about 4.1.

Aspect 118. The method of any one of Aspect 1-Aspect 117, wherein thecontacting the raw material with the first base is carried out in apond, a mixing, or combinations thereof.

Aspect 119. The method of any one of Aspect 1-Aspect 118, furthercomprising oxidation; wherein oxidation is mechanical oxidation,electrochemical oxidation, chemical oxidation, or combinations thereof.

Aspect 120. The method of Aspect 119, wherein oxidation comprises addingto the raw material and the first base an oxidizing agent.

Aspect 121. The method of Aspect 120, wherein the oxidizing agentcomprises a peroxide, ozone, a permanganate, or combinations thereof.

Aspect 122. The method of Aspect 121, wherein the oxidizing agent ishydrogen peroxide.

Aspect 123. The method of Aspect 122, wherein the hydrogen peroxide isadded in an mol amount that is equal to:Df×(Fe+(2×Mn)),

wherein Df is a number having a value of about 1.2 to about 1.5; whereinFe represents the mol amount of iron present; and Mn represents the molamount of manganese present.

Aspect 124. The method of any one of Aspect 1-Aspect 123, wherein thecontacting the raw material with the first base further comprises addinga flocculating agent, a coagulating agent, or combinations thereof.

Aspect 125. The method of any one of Aspect 1-Aspect 124, wherein theseparating the first aqueous phase from the first solid concentratecomprises using a clarifier, a settlement basin, or combinationsthereof.

Aspect 126. The method of any one of Aspect 1-Aspect 125, wherein thesecond base comprises a base selected from ammonium hydroxide, sodiumhydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide,ammonium carbonate, sodium carbonate, potassium carbonate, calciumcarbonate, magnesium carbonate, and a combination thereof.

Aspect 127. The method of Aspect 126, wherein the second base comprisescalcium hydroxide.

Aspect 128. The method of any one of Aspect 1-Aspect 127, wherein thecontacting the first aqueous phase with the second base is in an amountsufficient to adjust the pH to a value from about 8.0 to about 8.5.

Aspect 129. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is in an amount sufficient to adjustthe pH to a value from about 8.0 to about 8.4.

Aspect 130. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is in an amount sufficient to adjustthe pH to a value from about 8.0 to about 8.3.

Aspect 131. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is in an amount sufficient to adjustthe pH to a value from about 8.0 to about 8.2.

Aspect 132. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.0 to about 8.1.

Aspect 133. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.1 to about 8.5.

Aspect 134. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.1 to about 8.4.

Aspect 135. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.1 to about 8.3.

Aspect 136. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.1 to about 8.2.

Aspect 137. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.2 to about 8.5.

Aspect 138. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.2 to about 8.4.

Aspect 139. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.2 to about 8.3.

Aspect 140. The method of Aspect 128, wherein the contacting the firstaqueous phase al with the second base is an amount sufficient to adjustthe pH to a value from about 8.3 to about 4.5.

Aspect 141. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.3 to about 8.4.

Aspect 142. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.4 to about 8.5.

Aspect 143. The method of Aspect 128, wherein the contacting the firstaqueous phase with the second base is an amount sufficient to adjust thepH to a value from about 8.1 to about 8.2.

Aspect 144. The method of any one of Aspect 1-Aspect 39, wherein thecontacting the first aqueous phase with the second base is in an amountsufficient to adjust the pH to a value from about 7.5 to about 8.5.

Aspect 145. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base is in an amount sufficient to adjustthe pH to a value from about 7.6 to about 8.5.

Aspect 146. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.7 to about 8.5.

Aspect 147. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.8 to about 8.5.

Aspect 148. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.9 to about 8.5.

Aspect 149. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 4.0 to about 8.5.

Aspect 150. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.5 to about 8.4.

Aspect 151. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.6 to about 8.4.

Aspect 152. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.7 to about 8.4.

Aspect 153. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.8 to about 8.4.

Aspect 154. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.9 to about 8.4.

Aspect 155. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 4.0 to about 8.4.

Aspect 156. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.5 to about 8.3.

Aspect 157. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.6 to about 8.3.

Aspect 158. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.7 to about 4.3.

Aspect 159. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.8 to about 8.3.

Aspect 160. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.9 to about 8.3.

Aspect 161. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 4.0 to about 8.3.

Aspect 162. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.5 to about 8.2.

Aspect 163. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.6 to about 8.2.

Aspect 164. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.7 to about 8.2.

Aspect 165. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.8 to about 8.2.

Aspect 166. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.9 to about 8.2.

Aspect 167. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 8.0 to about 8.2.

Aspect 168. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.5 to about 8.1.

Aspect 169. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.6 to about 8.1.

Aspect 170. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.7 to about 8.1

Aspect 171. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.8 to about 8.1.

Aspect 172. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 7.9 to about 8.1.

Aspect 173. The method of Aspect 144, wherein the contacting the firstaqueous phase with the second base an amount sufficient to adjust the pHto a value from about 8.0 to about 8.1.

Aspect 174. The method of any one of 1-Aspect 173, wherein the HPC hassolids concentration from about 0.05% solids to about 5% solids.

Aspect 175. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 4.5% solids.

Aspect 176. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 4.0% solids.

Aspect 177. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 3.5% solids.

Aspect 178. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 3.0% solids.

Aspect 179. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 2.5% solids.

Aspect 180. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 2.0% solids.

Aspect 181. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 1.5% solids.

Aspect 182. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 1.0% solids.

Aspect 183. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 0.7% solids.

Aspect 184. The method of Aspect 174, wherein the HPC has solidsconcentration from about 0.1% solids to about 0.5% solids.

Aspect 185. The method of any one of 1-Aspect 184, further comprisingadding water or an aqueous solution to the HPC so that the solidsconcentration is from about 0.1% solids to about 1% solids.

Aspect 186. The method of any one of 1-Aspect 185, wherein thecontacting the first aqueous phase with the second base furthercomprises adding a flocculating agent, a coagulating agent, orcombinations thereof.

Aspect 187. The method of any one of 1-Aspect 186, wherein the removingthe aqueous effluent and the collecting a HPC comprises using aclarifier, a settlement basin, a flexible planar geotextile fabric ofwoven or nonwoven construction, or combinations thereof, or combinationsthereof.

Aspect 188. The method of any one of 1-Aspect 187, further comprising:(e) transferring the HPC to a geosynthetic geobag; and (f) conditioningthe HPC in the first conditioning tank for a period of time sufficientand a temperature suitable for the solids concentration in thegeosynthetic geobag to increase from 1.1-fold to about 15-fold comparedto the solids concentration of the HPC solids concentration.

Aspect 189. The method of Aspect 188, wherein the geosynthetic geobagcomprises woven materials, non-woven materials, or combinations thereof.

Aspect 190. The method of any one of 1-Aspect 187, further comprising:(e) transferring the HPC to a first conditioning tank; and (f) conditionthe HPC in the first conditioning tank for a period of time sufficientand a temperature suitable for the solids concentration in the lowersloped portion to increase from 1.1-fold to about 15-fold compared tothe solids concentration of the HPC solids concentration; therebyforming in the lower portion of the first conditioning tank a firstconditioned HPC.

Aspect 191. The method of Aspect 190, wherein the first conditioningtank is a plurality of two or more first conditioning tanks.

Aspect 192. The method of Aspect 190 or Aspect 191, wherein thetransferring is hydraulic pumping.

Aspect 193. The method of any one of Aspect 190-Aspect 192, wherein thefirst conditioning tank comprises an upper reservoir portion and a lowersloped portion; and wherein the sloped portion is an slope angle;wherein the sloped angle is an angle from about 15° to about 60° from ahorizontal normal perpendicular to the sides of the upper reservoirportion; and wherein the lower sloped portion comprises an outlet.

Aspect 194. The method of Aspect 193, wherein first conditioning tank isa cone conditioning tank; wherein the upper reservoir portion has acylindrical shape; and wherein the lower sloped portion has a rightcircular conical shape.

Aspect 195. The method of any one of Aspect 190-Aspect 194, wherein theperiod of time sufficient and the temperature suitable for the solidsconcentration in the lower sloped portion to reach a first conditionedpre-hydraulic solids concentration; wherein the first conditionedpre-hydraulic solids concentration is increased from 1.2-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration; wherein the period of time is from about 10 min to about72 hours; and wherein the temperature is from about 5° C. to about 50°C.

Aspect 196. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.3-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 197. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.4-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 198. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.5-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 199. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.6-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 200. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.7-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 201. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.8-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 202. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.9-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 203. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 2-fold to about10-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 204. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.1-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 205. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.2-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 206. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.3-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 207. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.4-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 208. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.5-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 209. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.6-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 210. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.7-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 211. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.8-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 212. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.9-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 213. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 2-fold to about7-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 214. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.1-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 215. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.2-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 216. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.3-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 217. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.4-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 218. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.5-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 219. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.6-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 220. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.7-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 221. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.8-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 222. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 1.9-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 223. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 2-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 224. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 2.5-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 225. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 3-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 226. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 3.5-fold to about5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 227. The method of Aspect 195, wherein the first conditionedpre-hydraulic solids concentration is increased from 3.5-fold to about4.5-fold compared to the solids concentration of the HPC solidsconcentration.

Aspect 228. The method of any one of Aspect 195-Aspect 227, wherein theperiod of time is from about 10 min to about 24 hours.

Aspect 229. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 12 hours.

Aspect 230. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 6 hours.

Aspect 231. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 3 hours.

Aspect 232. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 2 hours.

Aspect 233. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 90 minutes.

Aspect 234. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 80 minutes.

Aspect 235. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 70 minutes.

Aspect 236. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 60 minutes.

Aspect 237. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 50 minutes.

Aspect 238. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 40 minutes.

Aspect 239. The method of Aspect 228, wherein the period of time is fromabout 10 min to about 30 minutes.

Aspect 240. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 90 minutes.

Aspect 241. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 80 minutes.

Aspect 242. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 75 minutes.

Aspect 243. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 70 minutes.

Aspect 244. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 60 minutes.

Aspect 245. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 50 minutes.

Aspect 246. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 45 minutes.

Aspect 247. The method of Aspect 228, wherein the period of time is fromabout 30 min to about 40 minutes.

Aspect 248. The method of any one of Aspect 190-Aspect 247, furthercomprising collecting the first conditioned HPC.

Aspect 249. The method of Aspect 248, wherein the collecting comprisescollecting the first conditioned HPC to a tanker truck, a rail tankercar, a plurality of transport drums, or combinations thereof.

Aspect 250. The method of Aspect 248, wherein the collecting furthercomprises: (g) transferring the first condition HPC to a secondconditioning tank; and (h) condition the first conditioned HPC in thesecond conditioning tank for a period of time sufficient and at atemperature suitable for the solids concentration in the lower slopedportion to increase from 1.1-fold to about 5-fold compared to the solidsconcentration of the first conditioned HPC solids concentration; therebyforming in the lower portion of the second conditioning tank a secondconditioned HPC.

Aspect 251. The method of Aspect 250, wherein the transferring ishydraulic pumping.

Aspect 252. The method of Aspect 250 or Aspect 251, wherein the secondconditioning tank comprises an upper reservoir portion and a lowersloped portion; and wherein the sloped portion is an slope angle;wherein the sloped angle is an angle from about 15° to about 60° from ahorizontal normal perpendicular to the sides of the upper reservoirportion; and wherein the lower sloped portion comprises an outlet.

Aspect 253. The method of Aspect 252, wherein second conditioning tankis a cone conditioning tank; wherein the upper reservoir portion has acylindrical shape; and wherein the lower sloped portion has a rightcircular conical shape.

Aspect 254. The method of any one of Aspect 250-Aspect 253, wherein theperiod of time sufficient and the temperature suitable for the solidsconcentration in the lower sloped portion to increase from 1.2-fold toabout 5-fold compared to the solids concentration of the HPC solidsconcentration is a period of time from about 30 min to about 72 hours ata temperature of from about 5° C. to about 50° C.

Aspect 255. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.1-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 256. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.2-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 257. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.3-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 258. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.4-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 259. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.5-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 260. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.6-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 261. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.7-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 262. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.8-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 263. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.9-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 264. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 2-fold to about3-fold compared to the first conditioned HPC solids concentration.

Aspect 265. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.1-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 266. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.2-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 267. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.3-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 268. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.4-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 269. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.5-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 270. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.6-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 271. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.7-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 272. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.8-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 273. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 1.9-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 274. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 2-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 275. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 2.5-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 276. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 3-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 277. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 3.5-fold to about5-fold compared to the first conditioned HPC solids concentration.

Aspect 278. The method of Aspect 254, wherein the second conditionedpre-hydraulic solids concentration is increased from 3.5-fold to about4.5-fold compared to the first conditioned HPC solids concentration.

Aspect 279. The method of any one of Aspect 250-Aspect 278, wherein theperiod of time is from about 10 min to about 24 hours.

Aspect 280. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 12 hours.

Aspect 281. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 6 hours.

Aspect 282. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 3 hours.

Aspect 283. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 2 hours.

Aspect 284. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 90 minutes.

Aspect 285. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 80 minutes.

Aspect 286. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 70 minutes.

Aspect 287. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 60 minutes.

Aspect 288. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 50 minutes.

Aspect 289. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 40 minutes.

Aspect 290. The method of Aspect 279, wherein the period of time is fromabout 10 min to about 30 minutes.

Aspect 291. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 90 minutes.

Aspect 292. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 80 minutes.

Aspect 293. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 75 minutes.

Aspect 294. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 70 minutes.

Aspect 295. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 60 minutes.

Aspect 296. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 50 minutes.

Aspect 297. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 45 minutes.

Aspect 298. The method of Aspect 279, wherein the period of time is fromabout 30 min to about 40 minutes.

Aspect 299. The method of any one of Aspect 250-Aspect 298, furthercomprising collecting the second conditioned HPC.

Aspect 300. The method of Aspect 248, wherein the collecting comprisescollecting the second conditioned HPC to a tanker truck, a rail tankercar, a plurality of transport drums, or combinations thereof.

Aspect 301. The method of any one of Aspect 248, Aspect 249, Aspect 255,or Aspect 300, further comprising: transferring the first conditionedHPC or the second conditioned hydraulic pre-concentrate to mixing tank;adding a first acid to the mixing tank in an amount sufficient to adjustthe pH from about 2.0 to about 4.0; and wherein the first acid is mixedwith the first conditioned hydraulic pre-concentrate or the secondconditioned hydraulic pre-concentrate as the first acid is added;thereby forming PLS.

Aspect 302. The method of Aspect 301, wherein the acid is a mineralacid.

Aspect 303. The method of Aspect 302, wherein the mineral acid comprisesa mineral acid selected from nitric acid, hydrochloric acid, phosphoricacid, sulfuric acid, sulfurous acid, and combinations thereof.

Aspect 304. The method of Aspect 303, wherein the mineral acid comprisessulfuric acid.

Aspect 305. The method of any one of Aspect 301-Aspect 304, furthercomprising adding a flocculating agent, coagulating agent, orcombinations thereof.

Aspect 306. The method of any one of Aspect 301-Aspect 305, wherein thePLS is transferred to a filtration apparatus; and wherein the filtratecomprising a filtered PLS is collected.

Aspect 307. The method of Aspect 306, wherein the filtration apparatusis selected from bag filter, geo synthetic membrane, pan filter, plateand frame filter, drum filter, centrifuge, screw filter, hydrocyclone,and combinations thereof.

Aspect 308. The method of any one of Aspect 301-Aspect 307, wherein thePLS composition comprises lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;wherein each of the foregoing is independently present at aconcentration and sum of each concentration is a total rare earthelement concentration; and wherein the total rare earth concentration isabout 5 mg/L to about 500 mg/L.

Aspect 309. The method of Aspect 308, wherein the total rare earthconcentration is about 50 mg/L to about 500 mg/L.

Aspect 310. The method of Aspect 308, wherein the total rare earthconcentration is about 100 mg/L to about 500 mg/L.

Aspect 311. The method of Aspect 308, wherein the total rare earthconcentration comprises scandium at a concentration of from about 0.01mg/L to about 0.5 mg/L; yttrium at a concentration of from about 1.0mg/L to about 200 mg/L; lanthanum at a concentration of from about 0.01mg/L to about 5 mg/L; cerium at a concentration of from about 0.5 mg/Lto about 70 mg/L; praseodymium at a concentration of from about 0.1 mg/Lto about 15 mg/L; neodymium at a concentration of from about 0.5 mg/L toabout 80 mg/L; samarium at a concentration of from about 0.2 mg/L toabout 30 mg/L; europium at a concentration of from about 0.05 mg/L toabout 10 mg/L; gadolinium at a concentration of from about 0.2 mg/L toabout 50 mg/L; terbium at a concentration of from about 0.05 mg/L toabout 10 mg/L; dysprosium at a concentration of from about 0.2 mg/L toabout 50 mg/L; holmium at a concentration of from about 0.05 mg/L toabout 10 mg/L; erbium at a concentration of from about 0.1 mg/L to about30 mg/L; thullium at a concentration of from about 0.01 mg/L to about 3mg/L; ytterbium at a concentration of from about 0.05 mg/L to about 10mg/L; and lutetium at a concentration of from about 0.01 mg/L to about 1mg/L.

Aspect 312. The method of Aspect 308, wherein the total rare earthconcentration comprises scandium at a concentration of from about 0.05mg/L to about 0.15 mg/L; yttrium at a concentration of from about 20mg/L to about 45 mg/L; lanthanum at a concentration of from about 0.3mg/L to about 0.75 mg/L; cerium at a concentration of from about 5 mg/Lto about 15 mg/L; praseodymium at a concentration of from about 1 mg/Lto about 3.5 mg/L; neodymium at a concentration of from about 5 mg/L toabout 20 mg/L; samarium at a concentration of from about 2 mg/L to about7 mg/L; europium at a concentration of from about 0.5 mg/L to about 2mg/L; gadolinium at a concentration of from about 5 mg/L to about 15mg/L; terbium at a concentration of from about 0.5 mg/L to about 2 mg/L;dysprosium at a concentration of from about 4 mg/L to about 15 mg/L;holmium at a concentration of from about 0.5 mg/L to about 3 mg/L;erbium at a concentration of from about 2.5 mg/L to about 6 mg/L;thullium at a concentration of from about 0.2 mg/L to about 0.7 mg/L;ytterbium at a concentration of from about 0.7 mg/L to about 2.5 mg/L;and lutetium at a concentration of from about 0.05 mg/L to about 0.3mg/L.

Aspect 313. The method of any one of Aspect 250-Aspect 311, furthercomprising neutralizing the PLS or the filtered PLS by contacting thePLS or the filtered PLS with a third base in an amount sufficient toraise the pH of the PLS to a pH of from about 4.0 to 5.5, therebyforming a neutralized PLS.

Aspect 314. The method of Aspect 313, wherein the third base comprises abase selected from ammonium hydroxide, sodium hydroxide, potassiumhydroxide, calcium hydroxide, magnesium hydroxide, ammonium carbonate,sodium carbonate, potassium carbonate, calcium carbonate, magnesiumcarbonate, and a combination thereof.

Aspect 315. The method of Aspect 314, wherein the third base comprisesammonium hydroxide.

Aspect 316. The method of any one of Aspect 311-Aspect 315, wherein thecontacting the PLS or the filtered PLS with the third base is in anamount sufficient to adjust the pH to a value from about 4.0 to about5.1.

Aspect 317. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.0 to about 5.0.

Aspect 318. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.0 to about 4.9.

Aspect 319. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.0 to about 4.8.

Aspect 320. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.0 to about 4.7.

Aspect 321. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.0 to about 4.6.

Aspect 322. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.1 to about 5.0.

Aspect 323. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.1 to about 4.9.

Aspect 324. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.1 to about 4.8.

Aspect 325. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.1 to about 4.7.

Aspect 326. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.1 to about 4.6.

Aspect 327. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.2 to about 5.0.

Aspect 328. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.2 to about 4.9.

Aspect 329. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.2 to about 4.8.

Aspect 330. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.2 to about 4.7.

Aspect 331. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.2 to about 4.6.

Aspect 332. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.3 to about 5.0.

Aspect 333. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.3 to about 4.9.

Aspect 334. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.3 to about 4.8.

Aspect 335. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.3 to about 4.7.

Aspect 336. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.3 to about 4.6.

Aspect 337. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.4 to about 5.0.

Aspect 338. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.4 to about 4.9.

Aspect 339. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.4 to about 4.8.

Aspect 340. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.4 to about 4.7.

Aspect 341. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.4 to about 4.6.

Aspect 342. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.5 to about 5.0.

Aspect 343. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.5 to about 4.9.

Aspect 344. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.5 to about 4.8.

Aspect 345. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.5 to about 4.7.

Aspect 346. The method of Aspect 316, wherein the contacting the PLS orthe filtered PLS with the third base is in an amount sufficient toadjust the pH to a value from about 4.5 to about 4.6.

Aspect 347. The method of any one of Aspect 301-Aspect 346, wherein thePLS, the filtered PLS, or the neutralized PLS comprise iron at aconcentration less than or equal to about 25 mg/L.

Aspect 348. The method of any one of Aspect 301-Aspect 347, wherein thePLS, the filtered PLS, or the neutralized PLS comprise thorium anduranium in an aggregate concentration of less than about 1 mg/L.

Aspect 349. A PLS, a filtered PLS, or a neutralized PLS prepared by themethod of any one of Aspect 301-Aspect 348.

Aspect 350. A PLS composition comprising lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium,scandium, and yttrium; wherein each of the foregoing is independentlypresent at a concentration and sum of each concentration is a total rareearth element concentration; and wherein the total rare earthconcentration is about 5 mg/L to about 500 mg/L.

Aspect 351. The PLS of Aspect 350, wherein the total rare earthconcentration is about 50 mg/L to about 500 mg/L.

Aspect 352. The PLS of Aspect 350, wherein the total rare earthconcentration is about 100 mg/L to about 500 mg/L.

Aspect 353. The PLS of Aspect 350, wherein the total rare earthconcentration comprises scandium at a concentration of from about 0.01mg/L to about 0.5 mg/L; yttrium at a concentration of from about 1.0mg/L to about 200 mg/L; lanthanum at a concentration of from about 0.01mg/L to about 5 mg/L; cerium at a concentration of from about 0.5 mg/Lto about 70 mg/L; praseodymium at a concentration of from about 0.1 mg/Lto about 15 mg/L; neodymium at a concentration of from about 0.5 mg/L toabout 80 mg/L; samarium at a concentration of from about 0.2 mg/L toabout 30 mg/L; europium at a concentration of from about 0.05 mg/L toabout 10 mg/L; gadolinium at a concentration of from about 0.2 mg/L toabout 50 mg/L; terbium at a concentration of from about 0.05 mg/L toabout 10 mg/L; dysprosium at a concentration of from about 0.2 mg/L toabout 50 mg/L; holmium at a concentration of from about 0.05 mg/L toabout 10 mg/L; erbium at a concentration of from about 0.1 mg/L to about30 mg/L; thullium ata concentration of from about 0.01 mg/L to about 3mg/L; ytterbium at a concentration of from about 0.05 mg/L to about 10mg/L; and lutetium at a concentration of from about 0.01 mg/L to about 1mg/L.

Aspect 354. The PLS of Aspect 350, wherein the total rare earthconcentration comprises scandium at a concentration of from about 0.05mg/L to about 0.15 mg/L; yttrium at a concentration of from about 20mg/L to about 45 mg/L; lanthanum at a concentration of from about 0.3mg/L to about 0.75 mg/L; cerium at a concentration of from about 5 mg/Lto about 15 mg/L; praseodymium at a concentration of from about 1 mg/Lto about 3.5 mg/L; neodymium at a concentration of from about 5 mg/L toabout 20 mg/L; samarium at a concentration of from about 2 mg/L to about7 mg/L; europium at a concentration of from about 0.5 mg/L to about 2mg/L; gadolinium at a concentration of from about 5 mg/L to about 15mg/L; terbium at a concentration of from about 0.5 mg/L to about 2 mg/L;dysprosium at a concentration of from about 4 mg/L to about 15 mg/L;holmium at a concentration of from about 0.5 mg/L to about 3 mg/L;erbium at a concentration of from about 2.5 mg/L to about 6 mg/L;thullium at a concentration of from about 0.2 mg/L to about 0.7 mg/L;ytterbium at a concentration of from about 0.7 mg/L to about 2.5 mg/L;and lutetium at a concentration of from about 0.05 mg/L to about 0.3mg/L.

Aspect 355. The PLS composition of any one of Aspect 350-Aspect 354,wherein iron is present at a concentration less than or equal to about25 mg/L.

Aspect 356. The PLS composition of any one of Aspect 350-Aspect 355,wherein thorium and uranium are present in an aggregate concentration ofless than about 1 mg/L.

Aspect 357. The PLS composition of any one of Aspect 350-Aspect 356,wherein cobalt is present in an amount less than about 20 mg/L.

Aspect 358. A method for producing a PLS, the method comprising thefollowing steps: (a) contacting a raw material containing rare earthelements with a first base to form waste solids and an aqueous phase anddiscarding the waste solids; (b) contacting the aqueous phase with asecond base to form an REE-enriched preconcentrate and an effluent anddischarging the effluent; (c) contacting the REE-enriched preconcentratewith an acid to form an acidic preconcentrate; (d) filtering the acidicpreconcentrate to form an acidic filtrate; and (e) contacting the acidicfiltrate with a third base and filtering to form a PLS; wherein the PLSis enriched in rare earth elements and essentially free of solids.

Aspect 359. The method of Aspect 358, wherein the raw material is rawacid mine drainage (AMD), an AMD precipitate (AMDp), or an enriched AMDprecipitate (eAMDp).

Aspect 360. The method of Aspect 358 or Aspect 359, wherein contactingthe raw material with the first base changes the pH of the aqueous phaseto from about 4.0 to about 4.5.

Aspect 361. The method of any one of Aspect 358-Aspect 360, wherein thefirst base comprises NaOH, KOH, ammonia, ammonium hydroxide, calciumpellets, quicklime, lime slurry, or a combination thereof.

Aspect 362. The method of any one of Aspect 358-Aspect 361, whereincontacting the aqueous phase with the second base changes the pH of theaqueous phase to from about 8.0 to about 8.5.

Aspect 363. The method of any one of Aspect 358-Aspect 362, wherein thesecond base comprises NaOH, KOH, ammonia or an ammonium compound,calcium pellets, quicklime, lime slurry, or a combination thereof.

Aspect 364. The method of any one of Aspect 358-Aspect 363, wherein thecontacting the REE-enriched preconcentrate with the acid changes the pHof the REE-enriched preconcentrate to from about 0.7 to about 3.0.

Aspect 365. The method of any one of Aspect 358-Aspect 364, wherein theacid comprises hydrochloric acid, nitric acid, sulfuric acid, or acombination thereof.

Aspect 366. The method of any one of Aspect 358-Aspect 365, wherein step(c) further comprises contacting the REE-enriched preconcentrate and theacid with a reducing agent.

Aspect 367. The method of any one of Aspect 358-Aspect 366, whereincontacting the acidic filtrate with the third base changes the pH of theacidic filtrate to from about 2.8 to about 3.0.

Aspect 368. The method of any one of Aspect 358-Aspect 367, wherein thethird base comprises MgO, NaOH, KOH, ammonia or ammonium hydroxide,calcium pellets, quicklime, lime slurry, or a combination thereof.

Aspect 369. The method of any one of Aspect 358-Aspect 368, wherein step(e) further comprises oxidizing the acidic filtrate.

Aspect 370. The method of Aspect 369, wherein the acidic filtrate isoxidized mechanically, electrochemically, with an oxidizing agent, or acombination thereof.

Aspect 371. The method of Aspect 370, wherein the oxidizing agent ishydrogen peroxide.

Aspect 372. The method of Aspect 371, wherein the hydrogen peroxide isadded in an mol amount that is equal to:Df×(Fe+(2×Mn)),

wherein Df is a number having a value of about 1.2 to about 1.5; whereinFe represents the mol amount of iron present; and Mn represents the molamount of manganese present.

Aspect 373. The method of any one of Aspect 358-Aspect 372, furthercomprising a step for recovering scandium between steps (a) and (b), thestep for recovering scandium comprising contacting the aqueous phasewith a fourth base, thereby forming a scandium-enriched solidconcentrate, and removing the scandium-enriched solid concentrate fromthe aqueous phase.

Aspect 374. The method of Aspect 373, wherein contacting the aqueousphase with a fourth base changes the pH of the aqueous phase to fromabout 4.9 to about 5.1.

Aspect 375. The method of Aspect 373, wherein the fourth base comprisesNaOH, KOH, ammonia or an ammonium compound, calcium pellets, quicklime,lime slurry, or a combination thereof.

Aspect 376. The method of any one of Aspect 358-Aspect 375, furthercomprising adding a flocculating agent, a coagulating agent, or both inany of steps (a), (b), or (c).

Aspect 377. The method of any one of Aspect 358-Aspect 376, whereinfollowing step (e), the method further comprises subjecting the PLS tosolvent extraction to produce a refined rare earth resource comprisingat least 50% rare earth elements.

Aspect 378. The method of any one of Aspect 358-Aspect 377, wherein thePLS comprises lanthanum, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium, lutetium, scandium, and yttrium; wherein sum of eachconcentration of is a total rare earth element concentration; andwherein the total rare earth concentration is about 5 mg/L to about 50mg/L.

Aspect 379. The method of Aspect 378, wherein scandium is present at aconcentration of from about 0.05 mg/L to about 1 mg/L; yttrium ispresent at a concentration of from about 0.5 mg/L to about 10 mg/L;lanthanum is present at a concentration of from about 0.05 mg/L to about5 mg/L; cerium is present at a concentration of from about 0.5 mg/L toabout 7.5 mg/L; praseodymium is present at a concentration of from about0.05 mg/L to about 2.5 mg/L; neodymium is present at a concentration offrom about 0.5 mg/L to about 10 mg/L; samarium is present at aconcentration of from about 0.1 mg/L to about 2.5 mg/L; europium presentat a concentration of from about 0.05 mg/L to about 1.5 mg/L; gadoliniumis present at a concentration of from about 0.1 mg/L to about 5 mg/L;terbium is present at a concentration of from about 0.05 mg/L to about1.5 mg/L; dysprosium present at a concentration of from about 0.1 mg/Lto about 5 mg/L; holmium is present at a concentration of from about0.05 mg/L to about 2 mg/L; erbium is present at a concentration of fromabout 0.1 mg/L to about 5 mg/L; thullium is present at a concentrationof from about 0.05 mg/L to about 2 mg/L; ytterbium is present at aconcentration of from about 0.05 mg/L to about 5 mg/L; and lutetium ispresent at a concentration of from about 0.01 mg/L to about 1 mg/L.

Aspect 380. The method of Aspect 378 or Aspect 379, wherein iron ispresent at a concentration less than or equal to about 25 mg/L.

Aspect 381. The method of of any one of Aspect 378-Aspect 380, whereinthorium and uranium are present in an aggregate concentration of lessthan about 1 mg/L.

Aspect 382. The method of of any one of Aspect 378-Aspect 381, whereincobalt is present in an amount less than about 20 mg/L.

Aspect 383. The method of of any one of Aspect 378-Aspect 382, whereinthe PLS has a pH of from about 2.8 to about 3.0.

Aspect 384. A PLS composition enriched in rare earth elements andessentially free of solids made by the method of Aspect 358.

Aspect 385. The PLS composition of Aspect 384, wherein the PLS compriseslanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium, scandium, and yttrium; wherein sum of eachconcentration of is a total rare earth element concentration; andwherein the total rare earth concentration is about 5 mg/L to about 50mg/L.

Aspect 386. The PLS composition of Aspect 385, wherein scandium ispresent at a concentration of from about 0.05 mg/L to about 1 mg/L;yttrium is present at a concentration of from about 0.5 mg/L to about 10mg/L; lanthanum is present at a concentration of from about 0.05 mg/L toabout 5 mg/L; cerium is present at a concentration of from about 0.5mg/L to about 7.5 mg/L; praseodymium is present at a concentration offrom about 0.05 mg/L to about 2.5 mg/L; neodymium is present at aconcentration of from about 0.5 mg/L to about 10 mg/L; samarium ispresent at a concentration of from about 0.1 mg/L to about 2.5 mg/L;europium present at a concentration of from about 0.05 mg/L to about 1.5mg/L; gadolinium is present at a concentration of from about 0.1 mg/L toabout 5 mg/L; terbium is present at a concentration of from about 0.05mg/L to about 1.5 mg/L; dysprosium present at a concentration of fromabout 0.1 mg/L to about 5 mg/L; holmium is present at a concentration offrom about 0.05 mg/L to about 2 mg/L; erbium is present at aconcentration of from about 0.1 mg/L to about 5 mg/L; thullium ispresent at a concentration of from about 0.05 mg/L to about 2 mg/L;ytterbium is present at a concentration of from about 0.05 mg/L to about5 mg/L; and lutetium is present at a concentration of from about 0.01mg/L to about 1 mg/L.

Aspect 387. The PLS composition of any one of Aspect 384-Aspect 386,wherein iron is present at a concentration less than or equal to about25 mg/L.

Aspect 388. The PLS composition of any one of Aspect 384-Aspect 387,wherein thorium and uranium are present in an aggregate concentration ofless than about 1 mg/L.

Aspect 389. The PLS composition of any one of Aspect 384-Aspect 388,wherein cobalt is present in an amount less than about 20 mg/L.

Aspect 390. The PLS composition of any one of Aspect 384-Aspect 389,wherein the PLS has a pH of from about 2.8 to about 3.0.

Aspect 391. A PLS enriched in rare earth elements and essentially freeof solids, produced by the method comprising the following steps: (a)contacting a raw material containing rare earth elements with a firstbase to form waste solids and an aqueous phase and discarding the wastesolids; (b) contacting the aqueous phase with a second base to form anREE-enriched preconcentrate and an effluent and discharging theeffluent; (c) contacting the REE-enriched preconcentrate with an acid toform an acidic preconcentrate; (d) filtering the acidic preconcentrateto form an acidic filtrate; and (e) contacting the acidic filtrate witha third base and filtering to form a PLS.

Aspect 392. A method of preparing REE/CM oxides, the method comprising:providing a PLS as disclosed herein; extracting one or more REE/CM fromthe PLS via one or more solvent extraction steps, thereby preparingREE/CM oxides.

Aspect 393. The method of Aspect 392, further comprising the step ofreducing the REE/CM oxide to a reduced metal; wherein the step ofreducing comprises an electrowinning process, such as an electrolyticprocess; a metallothermic reduction process; or combinations thereof.

Aspect 394. The REE/CM oxide produced by Aspect 392.

Aspect 395. The reduced REE/CM produced by Aspect 393.

Aspect 396. A method for preparing a hydraulic pre-concentrate enrichedin rare earth elements and critical minerals, the method comprising: (a)contacting a raw material with a first base in an amount sufficient toadjust the pH to a value from about 4.0 to about 6.0, thereby forming amixture comprising a first aqueous phase and a first solid concentrate;(b) separating the first aqueous phase from the first solid concentrate;(c) contacting the first aqueous phase with a second base in an amountsufficient to adjust the pH to a value from about 7.0 to about 9.0,thereby forming a mixture comprising a second aqueous phase and thehydraulic pre-concentrate; (d) removing the second aqueous phase andcollecting the hydraulic pre-concentrate; wherein the raw materialcomprises rare earth elements; and wherein the hydraulic pre-concentrateis enriched in rare earth elements.

Aspect 397. The method of Aspect 396, wherein the raw material comprisesacid mine drainage associated with a coal mine, a hard rock mine, orcombinations thereof.

Aspect 398. The method of Aspect 397, wherein the acid mine drainageassociated with a coal mine, a hard rock mine, or combinations thereofis located at or proximal to the coal mine, the hard rock mine, orcombinations thereof.

Aspect 399. The method of Aspect 397, wherein the acid mine drainageassociated with a coal mine, a hard rock mine, or combinations thereofis transported to a location removed from the coal mine, the hard rockmine, or combinations thereof.

Aspect 400. The method of any of Aspect 397-Aspect 399, wherein the acidmine drainage is associated with a coal mine.

Aspect 401. The method of Aspect 396-Aspect 400, wherein the rawmaterial comprises raw acid mine drainage (AMD), an AMD precipitate(AMDp), an enriched AMD precipitate (eAMDp), or combinations thereof.

Aspect 402. The method of Aspect 401, wherein the raw material comprisesraw acid mine drainage (AMD).

Aspect 403. The method of Aspect 396-Aspect 402, wherein the rawmaterial has a pH less than about 4.0.

Aspect 404. The method of Aspect 396-Aspect 403, wherein the first basecomprises a base selected from ammonium hydroxide, sodium hydroxide,potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammoniumcarbonate, sodium carbonate, potassium carbonate, calcium carbonate,magnesium carbonate, and a combination thereof.

Aspect 405. The method of Aspect 404, wherein the first base comprisescalcium hydroxide.

Aspect 406. The method of Aspect 396-Aspect 405, wherein the contactingthe raw material with the first base is in an amount sufficient toadjust the pH to a value from about 4.0 to about 4.5.

Aspect 407. The method of Aspect 396-Aspect 406, further comprisingoxidation; wherein oxidation is mechanical oxidation, electrochemicaloxidation, chemical oxidation, or combinations thereof.

Aspect 408. The method of Aspect 407, wherein oxidation comprises addingto the raw material and the first base an oxidizing agent.

Aspect 409. The method of Aspect 408, wherein the oxidizing agentcomprises a peroxide, ozone, a permanganate, or combinations thereof.

Aspect 410. The method of Aspect 409, wherein the oxidizing agentcomprises hydrogen peroxide.

Aspect 411. The method of Aspect 410, wherein the hydrogen peroxide isadded in an mol amount that is equal to:Df×(Fe+(2×Mn)),

wherein Df is a number having a value of about 1.2 to about 1.5; whereinFe represents the mol amount of iron present; and Mn represents the molamount of manganese present.

Aspect 412. The method of Aspect 396-Aspect 411, wherein the second basecomprises a base selected from ammonium hydroxide, sodium hydroxide,potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammoniumcarbonate, sodium carbonate, potassium carbonate, calcium carbonate,magnesium carbonate, and a combination thereof.

Aspect 413. The method of Aspect 412, wherein the second base comprisescalcium hydroxide.

Aspect 414. The method of Aspect 396-Aspect 413, wherein the contactingthe first aqueous phase with the second base is in an amount sufficientto adjust the pH to a value from about 8.0 to about 8.5.

Aspect 415. The method of Aspect 396Aspect 414, wherein the removing theaqueous effluent and collecting the hydraulic pre-concentrate comprisesusing a clarifier, a settlement basin, a flexible planar geotextilefabric of woven or nonwoven construction, or combinations thereof.

Aspect 416. The method of Aspect 396-Aspect 415, further comprising: (e)transferring the hydraulic pre-concentrate to a geosynthetic geobag; and(f) conditioning the hydraulic pre-concentrate in a first conditioningtank for a period of time sufficient and a temperature suitable for thesolids concentration in the geosynthetic geobag to increase from about1.1-fold to about 15-fold compared to the solids concentration of thehydraulic pre-concentrate;

thereby forming in the geosynthetic geobag a first conditioned hydraulicpre-concentrate.

Aspect 417. The method of Aspect 416, wherein the geosynthetic geobagcomprises woven materials, non-woven materials, or combinations thereof.

Aspect 418. The method of Aspect 396-Aspect 417, further comprising: (e)transferring the hydraulic pre-concentrate to a first conditioning tank;and (f) conditioning the hydraulic pre-concentrate in the firstconditioning tank for a period of time sufficient and a temperaturesuitable for the solids concentration in the lower sloped portion toincrease from about 1.1-fold to about 15-fold compared to the solidsconcentration of the hydraulic pre-concentrate;

thereby forming in the lower portion of a conditioning tank a firstconditioned hydraulic pre-concentrate.

Aspect 419. The method of Aspect 418, wherein the conditioning tankcomprises a plurality of two or more conditioning tanks.

Aspect 420. The method of Aspect 418, wherein the conditioning tankcomprises a first conditioning tank and a second conditioning tank.

Aspect 421. The method of Aspect 418, wherein the period of timesufficient and the temperature suitable for the solids concentration inthe lower sloped portion to reach a first conditioned pre-hydraulicsolids concentration; wherein the first conditioned pre-hydraulic solidsconcentration is increased from about 1.2-fold to about 10-fold comparedto the solids concentration of the hydraulic pre-concentrate; whereinthe period of time is from about 10 min to about 72 hours; and whereinthe temperature is from about 5° C. to about 50° C.

Aspect 422. The method of Aspect 418, further comprising collecting thefirst conditioned hydraulic pre-concentrate.

Aspect 423. The method of Aspect 422, wherein the collecting furthercomprises: (g) transferring the first condition hydraulicpre-concentrate to a second conditioning tank; and (h) condition thefirst conditioned hydraulic pre-concentrate in the second conditioningtank for a period of time sufficient and at a temperature suitable forthe solids concentration in the lower sloped portion to increase fromabout 1.1-fold to about 5-fold compared to the solids concentration ofthe first conditioned hydraulic pre-concentrate; thereby forming in thelower portion of the second conditioning tank a second conditionedhydraulic pre-concentrate.

Aspect 424. The method of Aspect 423, wherein the period of timesufficient and the temperature suitable for the solids concentration inthe lower sloped portion to increase from about 1.2-fold to about 5-foldcompared to the solids concentration of the hydraulic pre-concentrate isa period of time from about 30 min to about 72 hours at a temperaturefrom about 5° C. to about 50° C.

Aspect 425. A method for preparing a pregnant leach solution, the methodcomprising: transferring the first conditioned hydraulic pre-concentrateof Aspect 418 or the second conditioned hydraulic pre-concentrate ofAspect 423 to a mixing tank; and adding a first acid to the mixing tankin an amount sufficient to adjust the pH from about 2.0 to about 4.0,thereby forming the pregnant leach solution; wherein the first acid ismixed with the first conditioned hydraulic pre-concentrate or the secondconditioned hydraulic pre-concentrate as the first acid is added.

Aspect 426. The method of Aspect 425, wherein the first acid is amineral acid.

Aspect 427. The method of Aspect 426, wherein the mineral acid comprisesa mineral acid selected from nitric acid, hydrochloric acid, phosphoricacid, sulfuric acid, sulfurous acid, and combinations thereof.

Aspect 428. The method of Aspect 427, wherein the mineral acid iscomprised of sulfuric acid.

Aspect 429. The method of Aspect 425, further comprising adding aflocculating agent, coagulating agent, or combinations thereof.

Aspect 430. The method of Aspect 425, wherein the pregnant leachsolution is transferred to a filtration apparatus; and wherein thefiltrate comprising a filtered pregnant leach solution is collected.

Aspect 431. The method of Aspect 425, further comprising neutralizingthe pregnant leach solution or the filtered pregnant leach solution bycontacting the pregnant leach solution or the filtered pregnant leachsolution with a third base in an amount sufficient to raise the pH ofthe pregnant leach solution to a pH of from about 4.5 to 5.0, therebyforming a neutralized pregnant leach solution.

Aspect 432. The method of Aspect 431, wherein the third base comprises abase selected from ammonium hydroxide, sodium hydroxide, potassiumhydroxide, calcium hydroxide, magnesium hydroxide, ammonium carbonate,sodium carbonate, potassium carbonate, calcium carbonate, magnesiumcarbonate, and a combination thereof.

Aspect 433. The method of Aspect 432, wherein the third base comprisesammonium hydroxide.

Aspect 434. The method of Aspect 431, wherein the neutralized pregnantleach solution comprises iron at a concentration less than or equal toabout 25 mg/L.

Aspect 435. The method of Aspect 431, wherein the neutralized pregnantleach solution comprises thorium and uranium in an aggregateconcentration of less than about 1 mg/L.

Aspect 436. A hydraulic pre-concentrate composition made by the methodof Aspect 396.

Aspect 437. A conditioned hydraulic pre-concentrate composition made bythe method of Aspect 423.

Aspect 438. A pregnant leach solution composition made by the method ofAspect 425.

Aspect 439. A method for preparing a pregnant leach solution, the methodcomprising: transferring a hydraulic pre-concentrate to a mixing tank;and adding a first acid to the mixing tank in an amount sufficient toadjust the pH from about 2.0 to about 4.0, thereby forming the pregnantleach solution; wherein the hydraulic pre-concentrate is enriched inrare earth elements compared to the rare earth elements concentrationpresent in an acid mine discharge; and wherein the first acid is mixedwith the hydraulic pre-concentrate as the first acid is added.

Aspect 440. The method of Aspect 439, wherein the acid is a mineralacid.

Aspect 441. The method of Aspect 440, wherein the mineral acid comprisesan acid selected from nitric acid, hydrochloric acid, phosphoric acid,sulfuric acid, sulfurous acid, and combinations thereof.

Aspect 442. The method of Aspect 441, wherein the mineral acid comprisessulfuric acid.

Aspect 443. The method of Aspect 439, further comprising adding aflocculating agent, coagulating agent, or combinations thereof.

Aspect 444. The method of Aspect 439, wherein the pregnant leachsolution is transferred to a filtration apparatus; and wherein thefiltrate comprising a filtered pregnant leach solution is collected.

Aspect 445. The method of Aspect 439, further comprising neutralizingthe pregnant leach solution or the filtered pregnant leach solution bycontacting the pregnant leach solution or the filtered pregnant leachsolution with a third base in an amount sufficient to raise the pH ofthe pregnant leach solution to a pH of from about 4.5 to 5.0, therebyforming a neutralized pregnant leach solution.

Aspect 446. The method of Aspect 445, wherein the third base comprises abase selected from ammonium hydroxide, sodium hydroxide, potassiumhydroxide, calcium hydroxide, magnesium hydroxide, ammonium carbonate,sodium carbonate, potassium carbonate, calcium carbonate, magnesiumcarbonate, and a combination thereof.

Aspect 447. The method of Aspect 446, wherein the third base comprisesammonium hydroxide.

Aspect 448. The method of Aspect 445, wherein the neutralized pregnantleach solution comprises iron at a concentration less than or equal toabout 25 mg/L.

Aspect 449. The method of Aspect 445, wherein the neutralized pregnantleach solution comprises thorium and uranium in an aggregateconcentration of less than about 1 mg/L.

Aspect 450. A pregnant leach solution composition made by the method ofAspect 439.

Aspect 451. A method for making a rare earth element oxide, the methodcomprising the steps of: providing a rare earth element oxide feedstockmaterial; subjecting the rare earth element oxide feedstock material toone or more solvent extraction steps; and isolating the rare earthelement oxide from the one or more solvent extraction steps; wherein therare earth element oxide feedstock material comprises a hydraulicpre-concentrate, a pregnant leach solution, or combination thereof.

Aspect 452. The method of Aspect 451, wherein the rare earth elementoxide feedstock material is obtained from an acid mine drainage.

Aspect 453. The method of Aspect 452, wherein the acid mine drainage isassociated with a coal mine, a hard rock mine, or combinations thereof.

Aspect 454. The method of Aspect 451, wherein the hydraulicpre-concentrate has solids concentration from about 0.05% solids toabout 5% solids.

Aspect 455. The method of Aspect 451, wherein the pregnant leachsolution comprises lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;wherein each of the foregoing is independently present at aconcentration and sum of each concentration is a total rare earthelement concentration; and wherein the total rare earth concentration isabout 5 mg/L to about 500 mg/L.

Aspect 456. The method of Aspect 451, wherein the rare earth elementoxide feedstock material comprises thorium and uranium in an aggregateconcentration of less than about 1 mg/L.

Aspect 457. The method of Aspect 451, wherein the hydraulicpre-concentrate has a pH of from about 7.0 to about 9.0.

Aspect 458. The method of Aspect 451, wherein the pregnant leachsolution has a pH of from about 2.0 to about 4.0.

Aspect 459. The method of Aspect 451, wherein the pregnant leachsolution has a pH of from about 4.0 to about 4.5.

Aspect 460. The method of Aspect 451, wherein the rare earth elementoxide is a rare earth element carboxylate.

Aspect 461. The method of Aspect 460, wherein the rare earth elementoxide is a rare earth element oxalate.

Aspect 462. The method of Aspect 451, further comprising the step ofreducing the rare earth element oxide to a reduced rare earth element;wherein the reducing is carried out using an electrolytic process, anelectrowinning process, or a metallothermic reduction process.

Aspect 463. A rare earth element oxide composition made by the method ofAspect 451.

Aspect 464. A reduced rare earth element made by the method of Aspect462.

Aspect 465. A method for making a rare earth element oxide, the methodcomprising the steps of: providing a rare earth element oxide feedstockmaterial; subjecting the rare earth element oxide feedstock material toone or more solvent extraction steps; and isolating the rare earthelement oxide from the one or more solvent extraction steps; wherein therare earth element oxide feedstock material comprises the hydraulicpre-concentrate of Aspect 396, the pregnant leach solution 28 or 39, orcombination thereof.

Aspect 466. The method of Aspect 465, wherein the rare earth elementoxide feedstock material is obtained from an acid mine drainage.

Aspect 467. The method of Aspect 466, wherein the acid mine drainage isassociated with a coal mine, a hard rock mine, or combinations thereof.

Aspect 468. The method of Aspect 465, wherein the hydraulicpre-concentrate has solids concentration from about 0.05% solids toabout 5% solids.

Aspect 469. The method of Aspect 465, wherein the pregnant leachsolution comprises lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;wherein each of the foregoing is independently present at aconcentration and sum of each concentration is a total rare earthelement concentration; and wherein the total rare earth concentration isabout 5 mg/L to about 500 mg/L.

Aspect 470. The method of Aspect 465, wherein the rare earth elementoxide feedstock material comprises thorium and uranium in an aggregateconcentration of less than about 1 mg/L.

Aspect 471. The method of Aspect 465, wherein the hydraulicpre-concentrate has a pH of from about 7.0 to about 9.0.

Aspect 472. The method of Aspect 465, wherein the pregnant leachsolution has a pH of from about 2.0 to about 4.0.

Aspect 473. The method of Aspect 465, wherein the pregnant leachsolution has a pH of from about 4.0 to about 4.5.

Aspect 474. The method of Aspect 465, wherein the rare earth elementoxide is a rare earth element carboxylate.

Aspect 475. The method of Aspect 474, wherein the rare earth elementoxide is a rare earth element oxalate.

Aspect 476. The method of Aspect 465, further comprising the step ofreducing the rare earth element oxide to a reduced rare earth elementoxide; wherein the reducing is carried out using an electrolyticprocess, an electrowinning process, or a metallothermic reductionprocess.

Aspect 477. A rare earth element oxide composition made by the method ofAspect 465.

Aspect 478. A reduced rare earth element made by the method of Aspect476.

From the foregoing, it will be seen that aspects herein are well adaptedto attain all the ends and objects hereinabove set forth together withother advantages which are obvious and which are inherent to thestructure.

While specific elements and steps are discussed in connection to oneanother, it is understood that any element and/or steps provided hereinis contemplated as being combinable with any other elements and/or stepsregardless of explicit provision of the same while still being withinthe scope provided herein.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

Since many possible aspects may be made without departing from the scopethereof, it is to be understood that all matter herein set forth orshown in the accompanying drawings and detailed description is to beinterpreted as illustrative and not in a limiting sense.

It is also to be understood that the terminology used herein is for thepurpose of describing particular aspects only, and is not intended to belimiting. The skilled artisan will recognize many variants andadaptations of the aspects described herein. These variants andadaptations are intended to be included in the teachings of thisdisclosure and to be encompassed by the claims herein.

Now having described the aspects of the present disclosure, in general,the following Examples describe some additional aspects of the presentdisclosure. While aspects of the present disclosure are described inconnection with the following examples and the corresponding text andfigures, there is no intent to limit aspects of the present disclosureto this description. On the contrary, the intent is to cover allalternatives, modifications, and equivalents included within the spiritand scope of the present disclosure.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompounds, compositions, articles, devices and/or methods claimed hereinare made and evaluated, and are intended to be purely exemplary of thedisclosure and are not intended to limit the scope of what the inventorsregard as their disclosure. Efforts have been made to ensure accuracywith respect to numbers (e.g., amounts, temperature, etc.), but someerrors and deviations should be accounted for. Unless indicatedotherwise, parts are parts by weight, temperature is in ° C. or is atambient temperature, and pressure is at or near atmospheric.

Example 1: Analytical Methods

ICP-MS was conducted using a Nexlon 2000-P instrument from Perkin Elmerequipped with an external Auto-diluter S400V from Elemental Scientific.Syngistic 2.4 software was used to collect and analyze data according tothe EPA 200.8 Rev. 5.4 method (1994).

ICP-OES was conducted on an ICP-OES 720 instrument from AgilentTechnologies using Expert II software according to method EPA 200.7 Rev.4.4 (1994).

A Gallery Discrete Analyzer System (CPQ-00096605 from Thermo FisherScientific) was used for some measurements including pH. Data wascollected and analyzed using Gallery software 6.0.1 according to methodSM 4500-E 2011.

Thermogravimetric was conducted using a TGA 801 instrument from LECOwith software package cornerstone version 2.8.8. The method used todetermine moisture levels was developed inhouse with sample beingbrought from room temperature to 105° C. and held to constant weight.

Acid digestion was a manual technique using a 1:1 ratio of nitric acidto sample. Additional data analysis for all techniques was conductedusing Microsoft Excel.

Example 2: Laboratory-Scale Experiments and Process Considerations

Laboratory experiments were performed prior to scaling up the disclosedprocess. Preliminary results produced solid feedstock with REE/CMaveraging 2.88% in the laboratory (see Table 4) to 0.2% in an initial,continuous field extraction trial. Of that amount, 0.14% were MREO,including the five REEs that are also CM (0.07%) and the criticalmineral cobalt (0.06%).

TABLE 4 Enrichment of Raw AMD Samples. REEs in Raw MREO Enrichment SiteAMD (μg/L) Grade (%) Factor AQ 51 738 1.30 17,615 AQ 2 352 2.08 59,091AQ 50 2119 2.20 10,382 AQ 8 2353 3.16 13,430 AQ 65 1300 5.65 43,439Average 1372 2.88 28,791

A field trial of a mobile version of the plant disclosed herein (seeFIG. 1 ) was deployed at a conventional AMD treatment plant referred toherein as the Omega Site. Preconcentrate from that plant (MREO=0.2%),when processed via ALSX, yielded a final MREO grade of 54.4% withoutacid washing (FIG. 2 ). In some experiments, acid washing increased MREOfrom 40% to either 62 or 80% by reducing the residual fraction byroughly one half. It is significant that the LREO and HREO were 35.3 and64.7% respectively while adding CM to the HREO yields 64.7%.

The disclosed plant and process featured a staged precipitation/AMDtreatment unit that concentrates REEs away from major gangue elementswhile simultaneously producing clean water for discharge. Significantgains in efficiency and cost were made by integrating AMD treatment withREE/CM recovery. Standard compliance-based AMD treatment raises the pHof the AMD from the inflow value (typically 2.5 to 3.5) to the finalvalue needed for discharge (7 to 8) in a single stage. This single-stepprecipitation can significantly concentrate REEs; however, it alsocaptures several problematic gangue metals into the sludge byproduct.Previous work focusing on REE extraction from sludge showed that thesegangue metals contribute to high transportation costs, high acidconsumption, and challenging separation.

In one aspect, a disclosed process focused on raw AMD in the earlystages of standard treatment and used staged precipitation to isolatethe REEs from the other gangue elements. A simplified process schematicfor performing this staged precipitation is shown in FIG. 3 . In thisdepiction, staged precipitation was achieved by using two reagent mixingunits and three clarifiers. Two parallel clarifiers (A and B) receivedAMD adjusted to the first pH setpoint provided by mixer A. This providesthe bulk of AMD treatment capacity. The underflow from clarifiers A andB largely consisted of iron and aluminum oxy-hydroxides and was disposedsimilarly to conventional AMD treatment byproducts, i.e., dewateringcells or GEOTUBE®. Mixer B increased the pH of the clarifier A and Boverflow to precipitate the REE/CM for removal in clarifier C. At thispoint in the circuit, the solid product was largely devoid ofdeleterious gangue metals and contained few acid consuming constituents.The underflow solids from clarifier C was a REE/CM preconcentrate thatwas dewatered and delivered to the ALSX plant for final concentration.Since the pH is raised to circumneutral values in the final stage, thethird clarifier overflow can be safely discharged to the environmentwhile meeting NPDES limits.

Testing showed that the disclosed process can effectively concentrateREE/CMs from raw AMD, with overall enrichment factors ranging from13,000× to 15,000×. More importantly, the process has proved to beextremely robust, as testing on different water feedstocks representinga variety of geochemical settings consistently produced similar resultswith respect to final REE purity. Other testing evaluated in theinfluence of raw water characteristics, alkaline material, pH endpoint,redox potential, and the use of flocculant, and the number of processstages. When optimized, these procedures consistently achieved REE/CMrecovery >96% and generated products with REE/CM grade consistentlybetween 0.1% to 5% wt %.

Specific testing of a host site focused on a single AMD source incontinuous run mode, as described in the Examples that follow. Theupstream concentrator was be evaluated on its ability to managevariations in flow and AMD concentration while satisfying threeparameters: NPDES permit compliance, operating costs and ability tosupply the ALSX plant with feedstock of adequate grade (about 0.1% to 5%MREO). The ALSX plant was evaluated based on operating cost and productgrade approaching or exceeding 35% to 95%. The added infrastructureincluded an additional clarifier in series with the two clarifiersnormally required of an AMD plant of this capacity. Also, independentlime dosing and additional materials handling can be utilized as neededto isolate the REE preconcentrate. Since the beginning and ending pHpoints for this process are similar to those of conventional AMDtreatment, the process added only modestly to base consumption. Thisoutcome was particularly favorable given the high consumable costs formany REE concentration strategies.

Table 5 illustrates the data analysis based on laboratory testing toidentify pH set points for the AMD/REE preconcentrator, based onlaboratory batch testing. Recovery to precipitate indicates the extentto which the major gangue elements are rejected at the early stages ofthe process while REEs are recovered to the final precipitate to a veryhigh degree (97%). With a grade of 48,015 mg REE/kg or 4.8%.

TABLE 5 Laboratory Extraction Testing at 3 pH Set Points. Recovery ofPrecipitate (%) Precipitate Concentration pH pH pH Element pH 4.0 pH 5.0pH 8.0 Total 4.0 5.0 8.0 Fe 373,600 2,436 7,253 383,289 97 1 2 Al 37,677235,055 35,704 308,435 12 76 12 S 52,100 72,459 7,107 131,666 4 55 5 Si4,623 13,504 98,068 116,195 4 12 84 Zn 50 478 110,268 110,796 0 0 100 Mn9,788 4,181 63,521 77,491 13 5 82 Mg 397 616 32,540 33,552 1 2 97 Ca1,296 2,387 9,930 13,613 10 18 73 Co 48 35 8,025 8,108 1 0 99 Ni 108 1095,710 5,927 2 2 96 Cd 20 0 138 158 12 0 87 Cl 0 11 95 106 0 11 89 Total479,706 331,271 378,358 1,189,336 40 28 32 Sc 18 59 18 95 19 62 19 Y 27325 13,307 13,659 0 2 97 La 7 15 3,597 3,618 0 0 99 Ce 136 127 8,9509,212 1 1 97 Pr 8 17 1,786 1,811 0 1 99 Nd 52 97 9,019 9,168 1 1 98 Sm15 45 2,386 2,446 1 2 98 Eu 3 13 586 602 1 2 97 Gd 14 67 3,473 3,554 0 298 Tb 2 13 450 465 0 3 97 Dy 10 86 2,286 2,382 0 4 96 Ho 2 16 415 422 04 96 Er 5 48 1,008 1,061 0 5 95 Tm 1 8 116 124 1 6 93 Yb 5 49 541 594 18 91 Lu 1 7 80 88 1 8 91 TREE 305 991 48,015 49,311 1 2 97 Th 158.7 6.20.9 165.9 95.7 3.8 0.6 U 1.8 22.3 96.1 120.2 1.5 18.6 80.0 TAc* 160.528.6 97.1 286.1 97.2 22.3 80.5 *Total actinides.

The incremental lime dosage rates and costs for the UpstreamConcentrator and resulting resource, grade and recovery were estimatedat each pH set point (Table 6). Based on two samples from an initialtesting site, this type of analysis can be used to quickly identify themost efficient pH set points based on operating cost, grade, andrecovery. This type of testing protocol and knowledge gained whileprocessing upstream concentrate samples through the disclosed ALSX plantminimized scaling risk as the AMD/REE is designed, installed, andoperated.

TABLE 6 Process Analysis: Two Runs at the Omega AMD Plant using Two pHSet Points. Run 1 Run 2 Raw pH Set Point Raw pH Set Point Parameter AMD4.0 AMD AMD 4.0 8.0 Acidity 302   116   30   461  53    46  Q (gpm)500   500   500   500  500   500  Acid 1813   698   178   2765   316  275  Load (lb/day) TMM 74  45   16   115  42    39  (mg/L) TREE 841  824   23   1319   1006     64  (μg/L) Acid 1813   698   178   2764  316   275  Load (tpd) Lime 1495   576   147   2279   261   227  DosingRate (lb/day) Lime $149.48 $57.58 $14.67 $227.5 $26.06  $22.68 Cost($/day) % Total 67%   26%    7% 82%    9%    8% Lime Cost TREE 102.8102.8  5681.8  991   48,015   Grade (mg/kg) TREE 5.21% 91.63% 30.92%65.41% Recovery

The disclosed processes involves an ALSX process that can further enrichthe REE preconcentrates to commercially attractive purity levels. Abench-scale solvent extraction system to extract REEs from AMDprecipitates and concentrate them into a final REO product was designed.The REEF on the WVU campus contained an acid leaching circuit, 100mixer-settler units, and downstream precipitation vessels. The systemhad integrated state-of-the-art sensors and controls provided byRockwell Automation (FIG. 4 ).

Bench-scale testing has allowed problems to be addressed prior to fullsite scale-up. Given the distribution and concentration of metals intypical AMD-based leachates, crud formation has proven to be a majornuisance in ALSX operation. Gangue element concentration was carefullymonitored during testing and leaching conditions were adjusted asnecessary. FIG. 5 shows SX operation with and without crud formation.

Data collected from this test facility demonstrated the technicalfeasibility of concentrating REEs from AMD-based feedstocks. Priortesting campaigns investigated the influence of several operationalvariables, including leaching pH, extractant concentration, organic toaqueous ratios, stripping acid type and concentration, precipitationconditions, and system feed flow rates. From this testing, optimaloperating conditions have been identified and the process has beenvalidated using three sources of run-of-mine AMD treatment solids.Sources include the Omega, DLM and Royal Scott AMD treatment plantsoperated by WVDEP. Resulting MREO concentrations ranged from 62 to 80%.

The PC from the upstream concentrator can be transported to an adjacentpilot-scale ALSX plant for final concentration to the high-grade MREOproduct. This approach includes several key changes from existing ALSXfacilities. First, these efforts represent an increase in project scale.The existing plant had a maximum production rate of 3 g/hr and thepilot-scale plant yielded about 15.5 g MREO/hr. Second, the solidfeedstock to the ALSX system is modified with the pilot scale ALSX beingfed by a preconcentrated feedstock from which most of the gangue metalshave been removed. This modification improved overall ALSX performance;prior laboratory-scale testing on preconcentrates from the stagedprecipitation process have shown that a 54% MREO product can begenerated from a single stage of solvent extraction (FIG. 2 ). Theexisting bench-scale REEF on the WVU campus has been used to runoff-line trials to optimize settings for the A34 (one site selected as asource) feedstock. In addition, the REEF facility has been used foradditional elemental-based separations such as those optimized torecover cobalt and scandium.

The disclosed AMD/REE process facility can be based on two criticalprocess technologies: 1) upstream concentration and 2) ALSX. A blockflow diagram showing the individual steps associated with each processis shown in FIG. 6 . None of the components of the disclosed processhave ever been integrated to extract REEs from AMD-based feedstocks in acommercial setting.

The upstream concentration development can be designed and operated as ascaled-down version of the AMD treatment facility deployable at a hostsite. The scaled unit was used to evaluate and optimize operatingparameters. The pilot-scale ALSX unit was designed to be approximately1/20^(th) the size of a full-scale unit.

The technical criteria defining project success are shown in Table 7.These values represent targets necessary for a commercial installation.To be competitive with other commercial REE resources (not includingscandium or other CMs), overall production costs must be on the order of$50 to $75/kg of REE produced. The target performance requirementsdefined in this table represent a combination that is expected toachieve this cost target.

TABLE 7 Performance Targets. Commercial Target Performance AttributePerformance Requirement REE recovery in leaching stage >80% REE recoveryin SX extraction stage >90% REE loss in scrubbing stage <10% REErecovery in SX stripping stage >85% REE preconcentrate trade >0.5% Grade of final MREO product >90% Actinide component of intermediate <1%of TREE content rare earth products Reagent consumption in acid leaching<100 kg/t of feed Solvent loss in solvent extraction <200 ppm Raffinaterecycle >25%

Example 3: Upstream Mobile Concentration Unit

A flow diagram of the constructed upstream mobile concentration plant isshown in FIG. 10 . Two circuits can be run in series or in parallelaccording to the disclosed design. In some experiments, a three-stageprecipitation scheme was employed by using an on-site treatmentclarifier as well as two circuits in the mobile plant; thisconfiguration is shown using a dotted line in the flow diagram. In otherexperiments, the two mobile circuits were run in parallel to maximizeproduction of precipitate using a two-stage precipitation procedure.After installation, shakedown testing was conducted to train the pHcontrollers to maintain a constant level in the two tanks.

A mobile plant as shown in FIG. 10 was plumbed into the system at theOmega AMD treatment plant, allowing for a split of clarified water to bepulled from the system's clarifier before discharge to settling orfinishing ponds. Supplemental chemical treatment was also installed sothat the Omega clarifier could operate at lower pH levels while stillmaintaining compliance with the NPDES outlet at the end of the finishingpond.

Elemental analysis of the products of the upstream concentration unitare shown in Table 8.

TABLE 8 Results from Operating Upstream Concentration Unit. AnalyteOmega Mobile Plant Mobile Plant Aqueous Feed Precipitated Product pH4.35 8 Major Ions mg/L mg/kg Al 27.95 190,382.11 Ca 354.09 21,825.29 Co0.15 515.65 Fe 2.51 16,990.35 Mg 28.19 3107.08 Mn 0.90 2630.15 Si 18.1779,936.27 SO₄ 1135.21 1374,75 TMM 1567.15 316,761.63 Rare Earth Elementsμg/L mg/kg Sc 9.48 66.37 Y 46.15 318.64 La 8.26 61.04 Ce 27.41 206.32 Pr4.33 31.84 Nd 21.66 154.70 Sm 6.27 45.87 Eu 1.62 12.21 Gd 9.65 71.68 Tb1.72 12.83 Dy 10.54 77.10 Ho 2.04 14.89 Er 5.57 40.83 Tm 0.73 5.59 Yb4.25 31.73 Lu 0.63 4.83 TREE 160.32 1156.45 Grade 0.000016% 0.12%Actinides μg/L mg/kg Th 0.14 1.69 U 2.33 12.16

Example 4: ALSX Bench-Scale Plant Operation

Process Overview

An ALSX plant was constructed to recover REEs from AMD precipitates. Theplant design was based on extensive acid leaching and solvent extractionlaboratory-scale studies. An initial system closely resembled theproposed design and shakedown testing was performed on each module ofthe plant to identify any construction or design oversights ranging fromminor leaks to improper component specification. Following testing,modifications to the overall process were instituted to overcome anyobserved obstacles.

After shakedown testing and plant modification, the ALSX plant wasplaced into operation by implementing a decoupled, semi-batch process.The bench-scale system includes three operating units: an acid leachingand filtration module, a solvent extraction module, and a precipitationmodule. Initially, small batches (˜60 L) of AMDp were converted to PLSusing the acid leaching portion of the plant. As the acid leachingtechnique was refined, larger batches were produced that could supplyfeedstock to the solvent extraction (SX) module for week-long runs. TheSX process was scheduled to operate in eight hour shifts for five daysper week until the PLS was exhausted.

Upon completion of the SX plant run, the stripped aqueous product wasprocessed using the precipitation module to convert the REE cations tooxalates. Next, the REE oxalate solids were calcined to transform theoxalates to oxides. After calcination, multiple washing stages wererequired to separate the REEs from gangue elements; therefore,increasing the grade of the final product. As a result of theseprocedures, a 62% mixed rare earth oxide material was acquired from theALSX plant.

Feedstock Acquisition and Material Handling

AMDp was collected from the proposed feedstock sites for processing inthe ALSX bench-scale plant. Ten 55-gallon drums of AMDp were collectedfrom each of the three AMD sites evaluated for this research. A smallexcavator was used to remove the AMDp from on-site storage ponds.Plastic drum liners were used to isolate the AMDp from the inside of thesteel drums. Upon delivery to the facility, the drums were stored in acontrolled environment until the material was required for leachingtests. Drums were placed on pallets at the time of loading. Once at theALSX facility, a pallet jack was employed to maneuver the drums into thestorage area. When required for leaching, the drums were maneuveredusing an overhead crane and tilting drum-lifting mechanism. Thisconfiguration was utilized to hoist the drums to the acid leachingmodule where the AMDp was removed from the lined drum and placed intofive-gallon buckets. Each of the buckets was individually weighed torecord the mass of AMDp before it was used in the acid leaching process.

Acid Leaching Module

The acid leaching module is located adjacent to the solvent extractionsystem. FIG. 11 shows the as-built acid leaching operating area. Theleaching vessels were operated under a full sized fume hood to preventoperator exposure to acidic fumes. The major components of the moduleinclude the fume hood, two 75-gallon agitated leaching mixing vessels, a420 mm filter press with a 2.0 cubic-foot capacity, air diaphragm pumps,and an acid dosing system. Directly outside the fume hood, a scale holdsa carboy of 68% nitric acid. The scale is used to monitor the amounts ofchemicals and feedstock consumed in the leaching process.

Acid Leaching Shakedown Testing

During the shakedown testing of the ALSX system, several operationaldifficulties were encountered when using the ALSX system as it wasinitially designed. As a result, modifications to the acid leaching flowdiagram were required to address these issues. The major operationalchallenges encountered and the flow diagram modifications implemented toovercome the unforeseen complications are presented below.

Gel Formation of PLS

During initial shakedown testing, several batches of PLS would form intoa gelatinous mixture when the pH was raised above the leaching pHset-point. This issue was observed in feedstock from all three AMDsites. FIG. 12 shows a representative sample of the gelatinous PLS afterpH adjustment. The formation of this gel inhibited pumping of the PLS.Additionally, the gel prevented filtering of the PLS; and therefore, theseparation of the solid and aqueous components of the leaching slurrywas impractical.

In order to alleviate this issue, several lab-scale experiments wereconducted to address the issue of gel formation. During testing, it wasdiscovered that the PLS did not form a gel when an additional filtrationstep was added to the procedure.

This extra filtration step was introduced directly after the PLS waslowered to the leaching pH value of 0.7. When tested on the acidleaching module, the additional filtration step prevented the congealingof the PLS at pH values less than 4.0. As a result, this additionalfiltration step was implemented into the operating procedure.

Filtration

Even in the absence of PLS gel formation, the vacuum pan filter wasunable to filter the PLS as it did not have a sufficient filtering areafor the amount of solid material remaining after acid leaching. Thiscondition was not addressed in the design phase because the small-scaletesting apparatus used did not allow for a proper evaluation of thefiltration. For example, leaching tests were conducted using vacuumfiltration with a Buchner funnel and filter paper. This operatingcondition did not produce a significant amount of precipitate toevaluate the bed depth and therefore the necessary filtration arearequired to perform an efficient solid-liquid separation.

To mitigate this issue, a bench-scale plate and frame filter press wereemployed to efficiently filter the PLS. Multiple batches of PLS werecreated using the three different feedstocks. Testing indicated that thefilter press was capable of filtering the PLS solutions from all of thefeedstocks at multiple pH values. Results from this experiment indicateda 2 cubic-foot filter press was of sufficient capacity to properlyfilter PLS from a 75-gallon agitated leach tank and create a clarifiedPLS. FIG. 13 shows a 150 mm lab-scale press used during testing and a420 mm filter press that later replaced the pan filter.

Full-scale testing with the 2 ft³ filter press was successful with allthree feedstocks as a direct result of the increased filtration area.Originally, the pan filter had a usable filtration area of 25 ft². Thenew filtration unit increased the filtration area by a factor of almost1.75 to 43 ft².

A Sandpiper S07 air diaphragm pump with a maximum capacity of 23 gpm wasused to feed the filter press. The pump was supplied with PVDF internalcomponents to resist the corrosion when pumping acidic liquids. Thefilter cake obtained from the filter press achieved moisture values ofapproximately 60%, which was substantially better than previous filtercakes acquired using vacuum filtration. FIG. 14 shows the PLS filtrateand the residual solids that remained after operation of the filterpress.

Acid Leaching Procedure and Results

After modifying the acid leaching process and equipment, an updatedprocess flow diagram was created as shown in FIG. 15 . The PLS createdfor the baseline Royal Scot solvent extraction test was made in twobatches. First, AMDp was added to the agitated leaching vessel,bucket-wise, so the mass of the AMDp could be recorded. Additionally, anAMDp sample was collected from each bucket and combined to form anoverall representative AMDp sample. The sample was then analyzed usingthermogravimetric analysis for moisture, ICP-MS for REEs, and ICP-OESfor major ion determinations. Second, water was added to the leachingvessel at 0.75 L per kg of as-received AMDp. This value was determinedempirically during shakedown testing to facilitate mixing, pumping, andfiltration of the PLS. Initial trials showed that using only AMDp andacid resulted in a thick slurry that was un-pumpable and thereforeunable to undergo the filtering process. Third, under rapid agitation,68% nitric acid was pumped into the leaching chamber until the desiredleaching pH set-point of 0.7. The pH was monitored using a hand-held pHmeter that was calibrated before the start of each batch. This processtook several hours for the vessel to achieve pH equilibrium. Finally,the low pH PLS was filtered using the 420 mm filter press.

After filtration, the clean PLS was pumped into a leaching vessel. Next,the pH of the PLS was adjusted upward with 50% sodium hydroxide, to a pHvalue of 3.0, to remove gangue metals. Once again, this process waspreformed step-wise over several hours until equilibrium was realized atthe desired pH set-point. Finally, the PLS was again filtered to removeany solids that precipitated during the upward pH adjustment. Thefiltrate from this process was sampled then transferred to the SX moduleas feed for the liquid-liquid extraction.

Table 9 shows the reagents and conditions implemented to create theRoyal Scot PLS. Combined, the two batches created a total of 282 litersof PLS for the subsequent SX process. The total acid consumption of theleaching procedure was 1.24 g acid/g feed. While the acid consumption ofthis batch process is high, other processes could be employed to reducethis metric. For example, countercurrent leaching could be employed toobtain a more efficient use of the leaching acid.

TABLE 9 Royal Scot Acid Leaching Parameters Used to Create PLS.Parameter Batch 1 Batch 2 Total AMDp Wet Mass (kg) 103.51 103.96 207.47AMDp Dry Mass (kg) 12.45 12.54 24.96 Water Volume (L) 75.60 75.60 151.20Initial pH 8.57 8.37 16.94 Acid Type 68% HNO₃ 68% HNO₃ 68% HNO₃ AcidAdded (kg) 24.07 21.32 45.39 Leach pH 0.59 0.75 0.67 Caustic Type 50%NaOH 50% NaOH 50% NaOH Caustic Added (kg) 8.71 8.44 17.15 Final pH 2.903.10 3.00 Final PLS Volume (L) 149.31 132.30 281.61 Filter Cake Wet Mass(kg) 33.75 36.02 69.76 Filter Cake Dry Mass (kg) 10.38 10.06 20.44 AcidConsumption (g acid/g ore) 1.31 1.16 1.24

Analytical testing was performed on the feed, concentrate, and tailingsof the comprehensive leaching process. These samples were analyzed usingICP-MS and ICP-OES methods to determine the REE concentrations and majorion concentrations, respectively. Tables 10A and 10B show the results ofthe analytical tests as well as the mass balance for both leachingbatches.

TABLE 10A Royal Scot Acid Leaching Assay and Mass Balance (Batch 1).Analyte Sludge Sludge PLS PLS Major Assay Mass Feed Mass Recovery Ionsmg/kg g mg/L g % Al 83,066.8 1034.4 2785.7 415.9 40% Ca 13,986.9 174.2734.7 109.7 63% Co 697.2 8.7 21.1 3.2 36% Fe 124,032.3 1544.5 4.0 0.6 0% Mg 57,207.9 712.4 2342.1 349.7 49% Mn 19,445.6 242.1 707.8 105.7 44%Si 29,654.3 369.3 62.1 9.3  3% SO₄ 8942.0 111.3 940.0 140.4 100%  Cl39.8 0.5 4.7 0.7 100%  TMM 337,072.8 4197.3 7602.1 1135.1 27% AnalyteRare Sludge Sludge PLS PLS Earth Assay Mass Feed Mass Recovery Elementsmg/kg mg μg/L mg % Sc 13.1 163.6 143.3 21.4 13% Y 343.1 4272.2 14,746.12201.7 52% La 67.9 845.8 3100.6 462.9 55% Ce 205.6 2560.0 8849.8 1321.452% Pr 34.7 432.3 1490.2 222.5 51% Nd 170.2 2119.5 7429.1 1109.2 52% Sm58.2 725.0 2427.4 362.4 50% Eu 15.2 189.4 617.6 92.2 49% Gd 86.8 1081.03623.2 541.0 50% Tb 13.8 171.7 555.4 82.9 48% Dy 75.0 933.8 3019.1 450.848% Ho 13.4 167.0 535.0 79.9 48% Er 35.2 438.3 1388.7 207.3 47% Tm 4.454.5 175.0 26.1 48% Yb 23.7 294.8 949.6 141.8 48% Lu 3.5 43.6 140.0 20.948% TREE 1163.8 14,492.4 49,190.0 7344.6 51% HREE 612.0 7620.5 25,275.43773.9 50% LREE 551.9 6872.0 23,914.6 3570.7 52% Analyte Filter CakeMajor Assay Filter Cake Mass Mass Balance Ions mg/kg g g Al 21,406.7222.1 396.3 Ca 2004.2 20.8 43.7 Co 87.3 0.9 4.6 Fe 152,369.3 1581.2 — Mg6645.2 69.0 293.7 Mn 5963.3 61.9 74.6 Si 25,952.8 269.3 90.7 SO₄ 1136.011.8 — Cl 76.4 0.8 — TMM 215,641.2 2237.8 903.6 Analyte Rare Filter CakeEarth Assay Filter Cake Mass Mass Balance Elements mg/kg mg mg Sc 11.5119.4 22.8 Y 39.3 408.3 1662.2 La 8.2 85.4 297.4 Ce 26.5 274.6 964.0 Pr4.4 45.9 163.9 Nd 21.4 221.6 788.7 Sm 7.1 74.1 288.5 Eu 1.9 19.3 77.9 Gd10.2 105.9 434.1 Tb 1.7 17.5 71.3 Dy 8.8 91.2 391.8 Ho 1.6 17.0 70.1 Er4.1 42.7 188.3 Tm 0.6 6.0 22.4 Yb 3.0 30.9 122.1 Lu 0.5 4.8 17.9 TREE150.8 1564.5 5583.4 HREE 81.3 843.6 3003.0 LREE 69.5 720.8 2580.5

TABLE 10B Royal Scot Acid Leaching Assay and Mass Balance (Batch 2).Analyte Sludge Sludge PLS PLS Major Assay Mass Feed Mass Recovery Ionsmg/kg g mg/L g % Al 83,066.8 1034.4 2848.4 425.3 41% Ca 13,986.9 174.2777.6 116.1 67% Co 697.2 8.7 24.8 3.7 43% Fe 124,032.3 1544.5 2.6 0.4 0% Mg 57,207.9 712.4 2387.5 356.5 50% Mn 19,445.6 242.1 862.0 128.7 53%Si 29,654.3 369.3 48.2 7.2  2% SO₄ 8942.0 111.3 875.0 130.6 100%  Cl39.8 0.5 4.5 0.7 100%  TMM 337,072.8 4197.3 7830.6 1169.2 28% AnalyteRare Sludge Sludge PLS PLS Earth Assay Mass Feed Mass Recovery Elementsmg/kg mg ug/L mg % Sc 13.1 163.6 212.3 31.7 19% Y 343.1 4272.2 15,472.82310.2 54% La 67.9 845.8 3293.4 491.7 58% Ce 205.6 2560.0 9138.1 1364.453% Pr 34.7 432.3 1555.4 232.2 54% Nd 170.2 2119.5 7766.7 1159.7 55% Sm58.2 725.0 2490.3 371.8 51% Eu 15.2 189.4 639.0 95.4 50% Gd 86.8 1081.03671.1 548.1 51% Tb 13.8 171.7 572.7 85.5 50% Dy 75.0 933.8 2964.6 442.647% Ho 13.4 167.0 540.8 80.8 48% Er 35.2 438.3 1384.5 206.7 47% Tm 4.454.5 173.2 25.9 47% Yb 23.7 294.8 948.2 141.6 48% Lu 3.5 43.6 134.8 20.146% TREE 1163.8 14,492.4 50,957.8 7608.5 52% HREE 612.0 7620.5 26,074.83893.2 51% LREE 551.9 6872.0 24,882.9 3715.3 54% Analyte Filter CakeMajor Assay Filter Cake Mass Mass Balance Ions mg/kg g g Al 21,145.3219.4 389.6 Ca 1833.8 19.0 39.0 Co 124.3 1.3 3.7 Fe 110,933.2 1151.2392.9 Mg 5895.5 61.2 294.7 Mn 7201.1 74.7 38.7 Si 24,190.7 251.0 111.0SO₄ 1369.6 14.2 — Cl 91.9 1.0 — TMM 172,785.3 1793.0 1269.7 Analyte RareFilter Cake Earth Assay Filter Cake Mass Mass Balance Elements mg/kg mgmg Sc 11.6 120.8 11.1 Y 42.1 437.0 1525.0 La 8.6 89.5 264.5 Ce 28.0290.5 905.1 Pr 4.7 48.7 151.4 Nd 23.9 248.0 711.8 Sm 7.9 82.1 271.1 Eu2.0 20.7 73.3 Gd 11.0 114.1 418.8 Tb 1.8 19.1 67.2 Dy 9.8 101.4 389.7 Ho1.8 18.6 67.7 Er 4.7 48.6 182.9 Tm 0.6 6.3 22.4 Yb 3.3 34.4 118.8 Lu 0.55.2 18.3 TREE 162.4 1684.9 5199.0 HREE 87.2 905.4 2821.9 LREE 75.1 779.62377.1

The analytical results revealed several significant outcomes resultingfrom the leaching process. Both leaching batches yielded PLS withgenerally similar concentrations of elements. Overall, approximately 51%of the REEs were recovered into the PLS solution, while only 27% of theother major ions were recovered, indicating a significant rejection ofgangue material. More noteworthy, the pH adjustment procedure resultedin the rejection of almost all of the Fe from the PLS. This issignificant as Fe can interfere with the subsequent SX process. Othergangue material was also rejected from the PLS including Al (40%), Ca(65%), Mg (50%), Mn (49%), and Si (3%).

Additionally, in regard to the REEs, the individual recoveries generallydecrease as the atomic number of the REE increases. Once exception tothis observation is Sc, which possesses a much lower average recovery of16%. The low recovery is not readily explained by standard thermodynamicconsiderations (e.g. Eh-pH diagrams) which indicate that Sc shouldremain in solution at pH values less than 6. Additionally, Sc is alsoreadily leached from other feedstocks using mineral acids. As a result,the current interpretation of these results is that other constituentswithin the PLS were causing interference with the Sc, resulting ineither precipitation at the pH value of less than 3.0 or preventing theSc from transferring to an aqueous phase with the acid digestion.

The overall mass balance of the acid leaching process indicated a largevariation between the balance and initial elemental masses ofapproximately 27% for the major ions and 37% for the rare earths. Thisdiscrepancy is quite large and indicative of analytical errors resultingfrom the sampling process or deficiencies existed in the measurement andrecording procedures. Furthermore, these types of mass balance errorshave been consistent throughout his research when using a saturated AMDpfeedstock. Previous research using thermogravimetric analysis to explorethe residual moisture in AMDp material after desiccation has indicatedthat some residual moisture may be left in the solid after traditionaldehydration methods. Given the high moisture contents of the feedstock,even a small change in moisture values could have a significant impacton the overall mass balance of the system.

Solvent Extraction Module

A bench-scale solvent extraction system with 100 individualmixer-settlers was acquired for this research. FIG. 16 shows the layoutof the bench-scale system. The constructed system was identical to theas-designed specifications developed in the planning phase of thisresearch. The overall SX plant consisted of ten individual stainlesssteel frames, with ten mixer-settlers attached to each frame, along withthe requisite pumps and chemical storage tanks needed for operation.

Multiple shakedown tests were performed on this system to empiricallyobtain a minimum set of operational parameters. Initially, a hydrostatictest was completed to identify any leaks in the system. Additionally,each unit's operation was evaluated during shakedown testing usingmultiple parameters to establish the key operating set-points requiredto perform the necessary process. This was accomplished by using PLSfrom each feedstock to test the extraction, scrubbing, stripping, andsaponification circuits in a batch-wise fashion until analytical testingshowed the circuit was preforming in a satisfactory manner. After themost promising parameters were identified, each feedstock was thenprocessed using the SX bench-scale plant in a continuous fashion todevelop a baseline result from which parametric testing could identifythe effect of changing individual SX parameters on the overallperformance of the plant.

Solvent Extraction Shakedown Testing

Throughout shakedown testing, several issues were noted that inhibitedthe operation of the bench-scale system. As each issue was discovered,changes were implemented to the as-designed system to alleviate thedeficiencies. Each operational challenge that was observed during thistesting regime is described below.

Third-Phase Crud Formation

During initial shakedown tests, two of the feedstocks (DLM and Omega)caused considerable third-phase formation as seen in FIG. 17 . Thisthird phase, also called crud, is a stable emulsion that causessignificant problems in the SX circuit. The crud encountered during thistesting began forming at the organic-aqueous interface and eventuallyoccupied most of the volume in the mixer-settler.

Before a continuous SX process flow diagram is finalized, a thoroughinvestigation of third phase formation is necessary. Issues encounteredduring the initial testing runs included difficulties in obtaining massbalances, organic loss to aqueous streams, and complete blockages oftubing connecting the mixer-settlers. Unfortunately, the generation oflarge amounts of crud renders parametric testing with these feedstocksdifficult, if not impossible, to complete.

Multiple exploratory tests were conducted in an attempt to prevent theformation of crud in the mixing chamber. These tests included dilutionof the PLS, use of the modifier tributyl phosphate, varying extractantconcentrations, and changing the extractant organic: aqueous (O:A)ratio. It was found that crud was caused by the gradual oxidation offerrous ion to the ferric form during solvent extraction. It was alsofound that addition of the oxidization agent hydrogen peroxide on aroughly 1:1 molar basis with ferrous ion concentration in PLS allowedprecipitation of all iron as ferric hydroxide during PLS preparation.This eliminated crud formation during solvent extraction.

When the PLS of the three feedstocks was compared, as shown in Table 11,it was evident that the Fe and Ca content in the Royal Scot PLS wasconsiderably lower than in the other two feedstocks. The currenthypothesis is that Fe or Ca will reach a limiting organic concentration(LOC) where the metal ions will start to precipitate and create anucleus that allows for crud formation. As a result, the Royal Scott PLSwas used to demonstrate this technology while DLM and Omega feedstockswere subjected to further leaching tests to remove the excess ganguemetals.

TABLE 11 Comparison of PLS from Three Feedstocks. Feedstock DLM OmegaRoyal Scot End pH 3.05 2.04 3.01 Major Ions (mg/L) Al 9480.84 3133.432982.86 Ca 1401.59 1372.56 761.02 Co 102.98 18.60 22.43 Fe 1936.00 71.433.18 Mg 6845.59 455.24 2426.65 Mn 3595.23 105.58 777.82 Na 47.5512,699.48 11,493.42 Si 1274.31 59.31 53.64 SO₄ 497.79 25.39 881.37 Cl17.92 5.65 4.67 TMM 25,199.80 17,946.67 19,407.05 Rare Earth Elements(μg/L) Sc 2118.11 962.45 <0.037 Y 83,061.09 7151.53 12,504.72 La23,908.46 1477.79 2646.17 Ce 64,313.63 4906.65 7519.84 Pr 8198.92 782.961248.48 Nd 34,781.11 3688.07 6330.98 Sm 8890.67 1133.53 2087.38 Eu2325.90 302.10 529.65 Gd 13,509.25 1820.15 3011.83 Tb 2239.51 339.07450.90 Dy 13,712.70 2016.94 2493.89 Ho 2713.13 381.42 444.83 Er 7453.571063.41 1162.19 Tm 965.45 144.99 136.08 Yb 5506.71 824.88 801.98 Lu793.23 125.05 104.29 Th 163.78 11.28 <0.007 U 815.79 257.11 198.47 TREE274,491.42 27,120.98 41,473.23 HREE 132,072.74 14,829.88 21,110.72 LREE142,418.68 12,291.10 20,362.51 CREE 136,120.30 13,497.71 22,310.15Maintaining Mixing Organic: Aqueous (O:A) Ratio

Another operational difficulty encountered in the operation of the SXplant involved maintaining a consistent O:A ratio in the mixing chamber.This issue was not observed in the SX unit operations that had anadvance ratio of 1:1. Conversely, unit operations that required high orlow O:A ratios often presented challenges in regard to maintaining aconsistent mixing O:A ratio. Two potential causes were identified.

First, overtime, the Tygon tubing used to recycle the aqueous phase inthe settler back to the mixer can become hardened and prevent operationof the roller-clamp that restricts flow in the recycle line. The secondissue is inherent to the roller clamp design. Often the roller-clampscould not provide the fine adjustment required to properly maintain thepreferred mixing O:A range of 1.5:1 to 1:1.5 as recommended by the SXplant manufacturer. To alleviate this issue, in-line valves wereinstalled into the recycle lines of the SX processes that requireadvance ratios greater than the recommended mixing range.

Organic Loss During Saponification

During initial shakedown testing, four unit operations were utilized(extraction, scrubbing, stripping, and saponification). During thesetests, a large fraction of the organic phase was reporting to thesaponification raffinate and not recycling back to the organic tank.Further research indicated that an additional stage was needed toseparate the organic and aqueous phases. As a result, the Megon RareEarth Circuit was referenced and an additional circuit (acid wash) wasimplemented directly after the saponification stage. This additionalstage greatly improved the recovery of organic to the organic recycletank.

While the addition of the acid wash circuit improved the recovery of theorganic to a level that was acceptable for the operation of thebench-scale plant, further modification may be necessary as the scale ofthe plant increases. Organic loss constitutes a significant cost forindustrial-scale SX operations. As a result, the addition of acoalescence device or other chemical modifier should be evaluated as thetechnological readiness level (TRL) of this process increases.

SX Procedure and Results

In order to develop a baseline test prior to parametric testing, a batchof PLS was processed in the SX system with an initial set of operatingparameters. Table 12 shows the parameters used in establishing thisbaseline test. The extractant, Elixore 205, is a highly-refinedaliphatic diluent, similar to kerosene, with a high flash point, lowviscosity, and ultra-low aromatic content. This diluent was chosen forthree reasons. First, standard kerosene was used in some initialshakedown testing; however, a strong odor was emitted by the kerosenethat permeated the enclosed area. Second, the use of a diluentspecifically designed for use in solvent extraction was necessary tominimize further scale-up issues as the TRL of the project increased.Third, previous phase separation tests showed a slight advantage inphase separation times with Elixore 205 versus other total diluents.

TABLE 12 Solvent Extraction Circuit Parameters for Baseline Testing.Parameter Value Extraction Organic Elixore 205 Extractantdi-(2-ethylhexyl)phosphoric acid Extractant concentration (M) 0.5Modifier tri-n-butyl phosphate Modifier concentration (v/v) 20% Advanceorganic:aqueous 1:1 Mixer speed (rpm) 856 Organic pump (mL/min) 75Aqueous pump (mL/min) 75 Scrubbing Reagent H₂O Concentration (v/v) 100%Organic:aqueous ratio 1:1 Mixer speed (rpm) 856 Scrub pump (mL/min) 75Stripping Reagent HCl Concentration (M) 6 Organic:aqueous ratio 10:1 Mixer speed (rpm) 856 Strip pump (mL/min) 7.5 Saponification ReagentNH₄OH Concentration 2 Organic:aqueous ratio 5:1 Mixer speed (rpm) 856Sap pump (mL/min) 15 Acid Wash Reagent HNO₃ Concentration (M) 0.75Organic:aqueous ratio 1:1 Mixer speed (rpm) 856 Acid wash pump (mL/min)75

Next, di-(2-ethylhexyl)phosphoric acid (D2EHPA) was chosen as theprimary extractant based on the wide industrial acceptance. Initialshakedown testing indicated third-phase crud formation occurred in theextraction, scrubbing, and stripping circuits. In order to address thisissue, tributyl phosphate (TBP) was added as a modifier.

The extraction and scrubbing advance O:A ratios were both set at 1:1 toprovide equal transfer of the REEs and gangue metals to the organicphase and scrubbing raffinate, respectively. For the stripping circuit,an O:A ratio of 10:1 was utilized to concentrate the REEs into thestripped raffinate, while minimizing the volume of the raffinate. Thiswas advantageous for the next process, as smaller volumes required lessmaterial handling. Finally, the saponification and acid wash O:A ratioswere of 5:1 and 1:1, respectively, based on previous shakedown testingresults. Mixer speeds were 856 rpm for every mixer in the SX plant.Lastly, every SX process was conducted using five mixer-settlers, withthe exception of the acid-wash stage where only three mixer-settlerswere utilized. This quantity is in excess of the number of stagesidentified in exploratory testing; however, using additional stagesreduces the effects of other system inefficiencies that may occur duringtesting. During parametric testing unit-by-unit sampling will lateridentify the critical number of stages required.

The plant was operated over a period of eight days with a totaloperating time of 58 hours. This equates to roughly 7.2 operating hoursper day or 90% operational availability. During this time, 281 liters ofthe PLS feedstock was processed through the system and concentrated into28.3 liters of stripped raffinate. Additionally, the organic phase wasconstantly recycled back to the extraction stage. This demonstrated theability of the process to run continuously, while showing that no metalions remained attached to the extractant; therefore, reducing theextraction rate in the first circuit. An aqueous sample was obtained atthe end of each operating day to evaluate the performance of the system.

FIG. 18 shows the process flow diagram of the ALSX system at the time oftesting. As previously discussed, the aqueous and organic phases werecirculated in a countercurrent fashion. Additionally, the organic phaseadvanced through each phase and was recycled for reuse at the end of theprocessing stream, after the saponification and acid wash stages.

In the extraction stage, the PLS and organic phases mix and settle,transferring REEs into the organic phase. Next, scrubbing removesunwanted elements from the organic while leaving the REEs in the organicphase using water or a mild acid. In the stripping stage, 6M HCl wasused to remove the REEs from the organic phase. In this stage a highadvance ratio was used to concentrate the REEs into the aqueous stripraffinate. Furthermore, the strip raffinate contained the valuableproduct from this operation that was used in the next plant module torecover the REEs. The last two stages, saponification and acid wash wereused to regenerate the extractant, cleaning the cation exchange sites oneach D2EHPA molecule.

Tables 13A and 13B below show the results of the daily analyticaltesting preformed on the PLS raffinate. While there was not a majorchange in the concentrations of the gangue material over the length ofthe test, it did take several days for the system to achieve steadystate in regard to consistent extraction of the REEs. During the firstthree days, several of the LREEs were not fully extracted. This could bea function of the pH within the mixing cell not reaching equilibrium.Conversely, the HREEs approached steady-state extraction at day 2.

TABLE 13A Extraction Stage Raffinate, Major Metals. (Site: Royal Scot,units mg/L) Day 1 2 3 4 Al 2646.6 3377.2 3258.0 3264.2 Ca 858.5 847.2783.5 850.9 Co 25.6 25.8 25.2 25.8 Fe 8.7 4.5 2.6 3.6 Mg 2639.8 2748.02707.7 2767.7 Mn 854.0 876.1 847.1 880.3 Na 12,474.2 11,879.7 11,011.911,321.0 Si 63.7 63.6 61.2 62.4 Total Major 19,571.0 19,822.1 18,697.219,176.0 Metals Day 5 6 7 8 Al 3408.3 3381.4 3313.2 3272.0 Ca 753.0737.6 674.1 657.1 Co 25.9 25.8 25.5 26.1 Fe 1.2 1.0 0.9 0.8 Mg 2790.32773.8 2732.8 2792.9 Mn 883.8 877.0 855.0 859.0 Na 13,388.0 12,206.811,957.5 11,684.6 Si 62.5 62.2 61.6 63.2 Total Major 21,313.0 20,065.519,620.6 19,355.6 Metals

TABLE 13B Extraction Stage Raffinate, REEs. (Site: royal Scot, unitsmg/L) Day 1 2 3 4 5 6 7 8 Sc <0.037 <0.037 <0.037 <0.037 0.3 0.6 0.5<0.037 Y 1435.3 529.4 221.3 66.3 77.6 21.4 41.7 43.5 La 3950.7 1135.638.8 17.0 63.6 32.1 31.5 24.5 Ce 7594.7 836.6 61.2 33.8 87.0 26.5 57.242.1 Pr 939.8 82.6 9.0 4.4 11.9 3.1 7.4 4.7 Nd 3884.6 323.5 46.3 20.654.6 13.3 33.9 20.4 Sm 290.9 55.7 14.5 5.9 12.7 2.0 5.5 2.4 Eu 53.3 15.44.0 1.7 3.2 0.6 1.2 0.5 Gd 318.4 89.9 23.6 9.5 16.9 2.8 5.6 2.6 Tb 40.616.2 4.8 1.9 2.5 0.5 0.9 0.5 Dy 242.4 101.2 34.6 12.2 15.1 3.3 6.1 5.1Ho 47.7 20.0 7.5 2.4 2.8 0.7 1.4 1.3 Er 136.4 51.9 24.0 7.1 8.1 2.2 4.35.1 Tm 16.7 5.0 3.0 1.0 1.0 0.4 0.6 0.9 Yb 89.1 19.6 14.1 5.3 3.3 1.22.2 5.6 Lu 11.1 2.2 1.7 0.8 0.4 0.2 0.4 0.8 Total 19,051.7 3284.7 508.6189.8 360.6 110.4 199.9 160.0 REEs

Additionally, the daily analytical testing results for the scrubbingraffinate are shown in Tables 14A and 14B below. This data indicatedthat there was some variation in the removal of chloride and sodium ionsfrom the extractant using water as a scrubbing medium. Additionally, thescrubbing stage did not reach a steady-state condition until after day4.

TABLE 14A Scrubbing Stage Raffinate, Major Metals. (Site: Royal Scot,units mg/L) Day 1 2 3 4 5 6 7 Al 9.4 1.1 17.2 4.0 29.1 0.8 0.6 Ca 19.20.4 43.3 14.0 53.7 5.8 4.6 Co 0.0 0.0 0.1 0.0 0.3 0.0 0.0 Fe 0.6 0.0 0.30.1 0.1 0.1 <0.022 Mg 7.5 0.1 16.0 6.7 37.2 7.5 8.1 Mn 6.3 0.0 13.4 13.761.4 7.3 5.5 Na 19.8 0.4 58.9 17.3 137.9 25.7 27.2 Si 3.0 0.5 3.0 2.32.8 2.3 2.3 Total Major 65.9 2.4 152.3 58.0 322.3 49.5 48.3 Metals

TABLE 14B Scrubbing Stage Raffinate, REEs. (Site: Royal Scot, unitsmg/L) Day 1 2 3 4 5 6 7 Sc <0.037 <0.037 <0.037 <0.037 <0.037 <0.037<0.037 Y 344.3 246.2 62.4 92.2 96.5 165.3 9.4 La 776.6 37.7 470.5 19.930.6 36.4 21.1 Ce 1098.4 104.1 429.7 47.9 50.9 107.0 62.2 Pr 125.7 17.549.1 7.7 7.5 17.9 10.2 Nd 501.5 91.2 203.1 39.0 37.1 91.3 51.9 Sm 42.830.3 23.6 13.0 11.4 30.4 15.0 Eu 9.6 8.0 4.7 3.4 3.4 7.9 3.5 Gd 58.047.3 24.6 19.7 19.8 44.6 18.2 Tb 10.6 8.4 2.5 3.1 3.5 6.8 1.8 Dy 66.250.1 13.0 18.1 21.5 37.3 6.1 Ho 12.5 9.2 2.3 3.3 3.9 6.6 0.7 Er 34.123.6 6.2 9.0 9.2 14.6 0.8 Tm 3.8 2.4 0.7 1.1 0.8 1.2 0.0 Yb 19.9 8.3 2.95.0 1.8 3.1 0.3 Lu 1.9 0.8 0.2 0.7 0.2 0.4 0.1 Total 3105.9 685.0 1295.7283.1 297.9 570.7 201.3 REEsPrecipitation Module

The precipitation module used to recover the REEs from the strippedraffinate is shown in FIG. 19 ; it is of a much smaller scale than theother ALSX plant equipment. The precipitation module consisted of anoverhead mixer used to agitate the stripped raffinate as reagents areadded to the solution. After precipitation, the striped raffinate isplaced in a ten-gallon conical bottom tank allowing the solids to settleat the bottom overnight. The use of the conical bottom tank minimizedthe volume of liquid that needed to be filtered. The last component ofthe precipitation module was a small pressure filter that separated thesolid and liquid components of the decanted stripped raffinate. Notshown are the drying oven and furnace used to dry and calcine the rareearth oxalates that precipitated from solution. This equipment was alsoused for the acid and water washing procedures described below.

Precipitation Procedure

After all of the PLS was processed through the solvent extraction plant,the stripping raffinate was collected for processing in theprecipitation module. FIG. 20 shows the process flow diagram thatresulted in the separation of a 62% mixed rare earth oxide product.After acquiring a headsplit of the stripped raffinate, 2.5 g/L of oxalicacid was added to the stripped raffinate, representing approximately 5times the stochiometric ratio of oxalic acid to REEs. Next, the pH ofthe stripped solution was raised with 50% NaOH to a value of 1.5. The pHadjustment was performed in multiple steps, ensuring the temperature ofthe solution did not exceed 80° Celsius.

Once the target pH was achieved, the solution was allowed to decantovernight until three quarters of the supernatant was left in thedecanting vessel and the remaining quarter was separated using apressure filter with Whatman Grade 40 ashless filter paper with anominal particle retention of 8 μm. Next, the precipitate was dried in aYamato DX602C oven at 105° Celsius. A sample was taken from theprecipitate and assayed to determine the REE content, as shown in Table15.

TABLE 15 Assay and Mass Balance of Initial Precipitation Steps. AnalyteStripped Stripped Precipitated Precipitated Raffinate Head- RaffinateRaffinate Filtrate Split Mass Filtrate Mass Volume (L) 28.32 42.28 Mass(g) 31.15 47.35 Major Ions mg/L g mg/L g Al 2626.16 74.37 1654.35 69.94Ca 897.55 25.42 17.41 0.74 Co 0.04 0.00 0.01 0.00 Fe 80.54 2.28 68.982.92 Mg 5.61 0.16 5.44 0.23 Mn 87.25 2.47 57.63 2.44 Si 7.75 0.22 5.890.25 SO₄ 8.76 0.25 0.33 0.01 TMM 3713.65 105.16 1810.04 76.52 Rare EarthElements μg/L g μg/L g Sc 0.02 0.00 0.44 0.00 Y 136,881.10 3.88 626.050.03 La 21,449.10 0.61 43.67 0.00 Ce 67,127.02 1.90 94.28 0.00 Pr11,125.33 0.32 11.66 0.00 Nd 55,454.65 1.57 45.22 0.00 Sm 18,654.50 0.5310.98 0.00 Eu 4953.41 0.14 2.76 0.00 Gd 28,813.05 0.82 18.64 0.00 Tb4538.49 0.13 4.58 0.00 Dy 25,609.26 0.73 43.73 0.00 Ho 4840.89 0.1415.10 0.00 Er 12,794.07 0.36 71.47 0.00 Tm 1677.06 0.05 14.55 0.00 Yb9270.63 0.26 104.95 0.00 Lu 1307.32 0.04 19.53 0.00 TREE 404,495.9011.46 1127.60 0.05 Actinides μg/L g μg/L g Th 9.52 0.00 5.52 0.00 U170.48 0.00 143.54 0.01 Analyte Precipitated Precipitated OxalateOxalate Mass Product Mass Balance Volume (L) Mass (g) 190.27 Major Ionsmg/kg g g Al 1122.60 0.21 4.21 Ca 138,002.05 26.26 (1.58) Co — — 0.00 Fe— — (0.64) Mg 31.26 0.01 (0.08 Mn 1388.97 0.26 (0.23 Si 211.41 0.04(0.07) SO₄ 450.09 0.09 0.15 TMM 141,206.38 26.87 1.77 Rare EarthElements mg/kg g g Sc — — — Y 20,068.41 3.82 0.03 La 3121.71 0.59 0.01Ce 9686.69 1.84 0.05 Pr 1620.39 0.31 0.01 Nd 8284.33 1.58 (0.01) Sm2658.68 0.51 0.02 Eu 711.38 0.14 0.00 Gd 4013.41 0.76 0.05 Tb 621.930.12 0.01 Dy 3533.09 0.67 0.05 Ho 648.16 0.12 0.01 Er 1746.58 0.33 0.03Tm 219.42 0.04 0.01 Yb 1249.35 0.24 0.02 Lu 170.32 0.03 0.00 TREE58,353.83 11.10 0.30 Actinides mg/kg g g Th 0.72 0.00 (0.00) U 0.75 0.00(0.00)

The oxalic acid precipitation process resulted in 190 g of precipitatecontaining 11.1 g of REEs. The represents a TREE recovery of 97%. Themajority of the measured major analytes were rejected during theprecipitation with the exception of Ca, which entirely co-precipitatedwith the REEs.

The REE oxalate precipitate was then calcined in a Lindberg mufflefurnace at a temperature of 750° Celsius for a duration of four hours. Asample of this material indicated the calcination procedure resulted inalmost doubling of the concentration of the REO product from 5.8% to 11%as shown in Table 16. Additionally, 22% of the dried product consistedof Ca. In order to further concentrate the REO product a series waterand acid washing steps were implements.

TABLE 16 Assay of Precipitation Cleaning Process. Analyte CalcinedCalcined Washed Washed Product Product Product Product Assay Mass AssayMass Mass (g) 94.36 68.5 Major Ions mg/lg g mg/kg g Al 2720 0.26 29570.20 Ca 222,201 20.97 277,119 18.98 Co 1 0.00 2 0.00 Fe 116 0.01 74 0.01Mg 232 0.02 74 0.01 Mn 2433 0.23 2734 0.19 Si 735 0.07 269 0.02 SO₄ 1880.02 4 0.00 TMM 7521 0.71 4 0.00 Rare Earth Elements mg/kg g mg/kg g Sc— — — — Y 37,128 3.50 41,428 2.84 La 5712 0.54 6652 0.46 Ce 17,251 1.6318,798 1.29 Pr 2916 0.28 3442 0.24 Nd 15,021 1.42 17,749 1.22 Sm 50410.48 5805 0.40 Eu 1293 0.12 1562 0.11 Gd 7416 0.70 9094 0.62 Tb 11490.11 1429 0.10 Dy 6546 0.62 8035 0.55 Ho 1218 0.11 1559 0.11 Er 32540.31 4064 0.28 Tm 412 0.04 539 0.04 Yb 2301 0.22 2890 0.20 Lu 317 0.03410 0.03 TREE 106,975 10.09 123,455 8.46 Grade 11% 12% Actinides mg/kg gmg/kg g Th 8 0.00 8 0.00 U 6 0.00 6 0.00 Analyte Acid Wash Acid WashProduct Product Acid Wash Assay Mass Oxide Basis Mass (g) 13.8 MajorIons mg/kg g mg/kg Al 12,216 0.17 19,456 Ca 76,540 1.06 91,848 Co 3 0.003 Fe 748 0.01 961 Mg 85 0.00 113 Mn 13,947 0.19 15,975 Si 673 0.01 865SO₄ 183 0.00 183 TMM 20 0.00 20 Rare Earth Elements mg/kg g mg/kg Sc — —— Y 173,858 2.40 198,805 La 24,773 0.34 29,053 Ce 95,650 1.32 117,494 Pr14,606 0.20 17,646 Nd 74,811 1.03 87,259 Sm 25,532 0.35 29,607 Eu 65950.09 7637 Gd 36,883 0.51 42,512 Tb 6019 0.08 7079 Dy 33,201 0.46 38,104Ho 6099 0.08 6986 Er 16,236 0.22 18,566 Tm 2153 0.03 2458 Yb 11,867 0.1613,512 Lu 1652 0.02 1879 TREE 529,933 7.31 618,598 Grade 53% 62%Actinides mg/kg g mg/kg Th 53 0.00 57 U 40 0.00 44

The washing procedure consisted of multiple washing cycles. Afterdecanting and filtering, the REO product was agitated in 1 L ofdeionized water for thirty minutes. This procedure was repeated untilthe conductivity of the supernatant was below 50 μS/cm. In all, tenwashing cycles were completed. Following washing, analysis of a sampleof the REO product indicated that only small portions of the ganguematerial Ca (2 g) and CI (0.7 g) were removed. As a result, a moreintense washing procedure was implemented, where the pH of the washwater was lowered to a pH of 3.5 to remove the remaining Ca.

Next, the REO product was subjected to an acid wash. This was conductedby placing the REO product in 1 L of deionized water and the pH waslowered using 3M nitric acid until a pH value of 3.5 was obtained.During this procedure, a notable effervesces occurred as the pH lowered.After washing and drying of the residual solid material, a noticeableloss of mass was observed as the sample was reduced from 68. g to 13.8g. ICP-MS analysis confirmed the majority of the Ca was removed.

FIG. 21 shows the resulting rare earth oxide product produced the ALSXplant. The material consisted of a fine powder that was slightly gray incolor.

Example 5: Economic Analysis

The nominal AMD feed rate of the disclosed plant is 500 gpm with amaximum capacity of 1,000 gpm. Ideal REE production is projected to be1,000 kg MREO/year or 110 g MREO/hr. The plant treats all of theapproximately 456 tons of acid load in the AMD stream per year with anestimated lime consumption cost of $65,000/year. At a contained value of$237/kg MREO, the annual yield can generate annual revenue of about$237,000, which is more than enough to cover the cost of AMD treatment.The plant is configured so that its AMD treatment train can operateindependently and without performance degradation regardless of whetherthe REE recovery process is operating on a given day. In one aspect, thedisclosed processes allow the plant's operator to maintain its CleanWater Act compliance obligations independently of REE recovery.

In addition to treating AMD and generating a preconcentrate, thedisclosed plant includes a continuous acid leaching/solvent extractiontrain at its downstream end that can produce a MREO grade exceeding 90%.Production capacity is estimated to equal 15.5 g MREO/hour (Table 17).

TABLE 17 Estimated MREO Production for Proposed Facility. UpstreamConcentrator Product Grade  1% MREO Recovery 90% Upstream Concentrate803.6 kg MREO/year 82.6 g MREO/hour ALSX Product Grade 90% MREO Recovery75% Ideal Yield 61.9 g MREO/hour Availability 25% Estimated Yield 15.5 gMREO/hour

In some cases, the REE resource at individual AMD treatment sites andindividual AMD sludge ponds may be limited. Results from a regionalsurvey showed that the REE flux from an average AMD outfall is only 400kg/year, while the average sludge pond contains less than 10,000 kg REEin total. In some aspects, neither of these values are large enough tojustify a commercial-scale REE concentration and refining plant at asingle AMD treatment site. However, in some cases, a dispersed networkof on-site handling operations can be integrated to feed a centralizedALSX system. In a feasibility study, it was shown that a 2,100 TPD ALSXfacility processing raw AMD sludge has the potential to produce an IRRof 37% and a net present value of $80 million over a 20-year operatingperiod. The total capital cost for this plant is $46 million and theoperating cost is $141/kg.

A detailed techno-economic analysis showed that these favorable resultsare sensitive to sludge acid consumption and sludge feed moisture. Forexample, FIG. 7 (top) shows the maximum possible acid dose required tokeep the total acid cost below an economic threshold of $100/kg as afunction of REE feed grade and leaching recovery. As shown, raw sludge(˜0.6% REE, ˜75% recovery) can only be processed in a cost-effectivemanner if the maximum acid dose is on the order of 100 to 150 kg/t. FIG.7 (bottom) shows a similar analysis whereby the maximum haulage distanceneeded to keep the total shipping cost below 5% of the feedstockcontained value (CV) has been determined as a function of feed grade andfeed moisture. For raw sludge (0.6% REE, 50-80% moisture), the maximumhaulage distance is nearly negligible—less than 10-15 miles.

Traditional compliance-based treatment of AMD tends to push both thesludge acid consumption and the sludge moisture to unfavorable values.Many AMD treatment operators tend to overdose lime addition to avoidnon-compliant discharges. This practice leaves large quantities ofunreacted lime in the final precipitate, and this base must be fullyconsumed during the acid leaching step of treatment processes at asignificant cost to the REE producer. Moreover, traditional sludgedrying cells are ineffective at reducing sludge moisture, and many ofthe sludge samples evaluated in our prior studies have values exceeding80-90%. Both issues are problematic for commercialization as they reducethe number of viable sludge sites that meet thresholds for economicviability. Sludge samples that do not meet the economic thresholds areconsidered stranded resources and are not considered relevant to aregional production scenario. When taken together these results indicatethat the hypothetical 2,100 tons per day (TPD) ALSX plant describedherein may have difficulty identifying a sufficient quantity of rawsludge feedstock that meet these criteria. A reduction in total plantthroughput will inevitably lead to a proportional reduction in economicoutcomes.

However, the upstream concentration process described herein offers acomprehensive solution to these issues. Most significantly, the upstreamconcentrator will increase the grade of the ALSX feed by rejecting ironand aluminum during the standard water treatment process. FIG. 7 showsthe drastic influence that the increased feedstock grade will have onmaximum acid dose (>4,000 kg/t) and maximum haulage distance (increasedto >200 miles). In addition to the simple grade increase, the upstreamconcentrator provides better pH control technology to mitigate the acidconsumption issues associated with overdosed lime addition; moreover,the use of GEOTUBE® will assist in reducing product moisture. All thesefactors substantially reduce ALSX processing costs, while simultaneouslyincreasing the quantity of feedstock meeting the economic thresholds. Ifwidely implemented across the Appalachian region, the AMD/REEpre-concentration plants will ensure a consistent and reliable supply offeedstock for ALSX operations.

This techno-economic analysis (TEA) has used standard economicguidelines provided by NETL and incorporates the most recent processknowledge regarding the disclosed ALSX process. Since the upstreamconcentrator can be easily integrated into existing AMD treatmenttechnologies, the capital and operating costs for this process areassumed to be external to the REE producing entity and are not includedin the analysis; however, an additional $50/t feedstock acquisition costis included to account for any additional reagent addition,capitalization expenses, or handling needed to deliver thepre-concentrate to the ALSX plant. The results of this analysis areshown in Table 18 for a nominal 175 TPD plant.

TABLE 18 Economic Indicators for Commercial ALSX System. EconomicParameter Value Plant feed rate/grade 175 TPD at 2% REE Productrate/grade 2 TPD at 90% MREO Operating period 20 years; 10% discountrate REE basket price $147/kg REE recovery 59% Plant capital expenses$20 million Plant operating expenses $54/kg Net present value $80million Internal rate of return 61% Payback period 1.5 operating years

The results confirm the economic gains inherent to the upstreamconcentration prior to ALSX. Compared to the prior scenario, whichtreated raw sludge, the current model output shows that a similar NPV($80 million) can be achieved at a much smaller overall plant size (175TPD vs. 2,100 TPD). The smaller plant also entails a much lower capitalcost and a lower operating cost, $20 million and $54/kg REErespectively. While both scenarios have been shown to be economicallyfavorable, the pre-concentrated route is much more viable from acommercial perspective, owing to the smaller feedstock requirement andreduced capital cost. Both of these items reduce overall project riskand are thus more favorable for investment. In addition, FIG. 8 shows asensitivity analysis of operating cost with respect to both feed gradeand plant size. As shown, for most plant sizes, the largest incrementalreduction in operating cost is achieved.

Other matters pertaining to commercialization include permitting andregulatory factors, downstream refining capacity, and REE pricingfactors. Wastes from the disclosed processes can be easily integratedinto the existing infrastructure without the need for new permits. Thisoutcome is also desirable for commercialization, as it minimizes thestartup time needed to initiate new projects. With regard to refiningcapacity, the US currently has no domestic facilities that can producerefined REE products from mixed REOs. In one aspect, disclosed herein isthe generation of REO concentrates, which can be used in downstreamrefining studies. With regard to pricing, all of the economic results inTable 17 have been determined using a price discount of 50% relative tothe standard oxide prices provided by NETL. This price discount accountsfor charges from downstream refining and also indicates that the processcan still be profitable despite price volatility.

Example 6: Removal of Gangue Elements

Removal of gangue elements in an AMD feedstock during preparation of adisclosed PLS using the foregoing methods is further illustrated inTable 19 below. The data therein shows that at the first pH step 712,aluminum and iron are significantly removed, and at the second pH step718, REE and cobalt are removed from the aqueous phase, i.e., theeffluent 724, and are recovered in the REE-enriched pre-concentrate.

TABLE 19 Removal of Gangue Elements. Aqueous phase AQ65 Analyte RawWater pH 4.7 pH 8.5 Al mg/L 25.5 2.3 0.1 Fe mg/L 0.701 0.018 0.053 Mnmg/L 11.8 10.6 9.3 Ni mg/L 0.4 0.4 0.3 Si mg/L 9.1 8.1 6.0 Zn mg/L 1.21.1 0.0 Ca mg/L 70.2 119.0 133.1 Mg mg/L 38.1 37.0 37.1 Na mg/L 1.6 1.61.7 SO₄ mg/L 494.5 497.9 483.6 Cl mg/L 0.0 0.0 0.4 total mg/L 653.1678.1 671.7 Sc ug/L 5.6 0.9 0.1 Y ug/L 174.5 157.0 0.3 La ug/L 40.0 37.80.3 Ce ug/L 89.8 79.8 0.1 Pr ug/L 19.0 17.9 0.0 Nd ug/L 98.0 89.0 0.2 Smug/L 27.3 24.4 0.0 Eu ug/L 6.9 6.2 0.0 Gd ug/L 41.0 36.3 0.0 Tb ug/L 5.95.3 0.0 D ug/L 31.9 27.9 0.0 Ho ug/L 6.1 5.3 0.0 Er ug/L 16.1 13.7 0.0Tm ug/L 2.0 1.7 0.0 Yb ug/L 11.1 9.2 0.0 Lu ug/L 1.6 1.3 0.0 TREE ug/L576.8 513.7 1.1 Co mg/L 0.4 0.4 0.2 TREE + Co mg/L 577.3 514.1 1.3

The disclosed process results in removal of gangue elements at the firstpH step 712, e.g., aluminum, iron, and silicon; while concentrating REEand cobalt in the pre-concentrate after the second pH step 718.

Example 7: Preparation of Hydraulic Pre-Concentrate (HPC) from Raw AcidMine Drainage (AMD) Water

An approximately 5,000 gallon load of untreated acid mine drainage (AMD)comprising ˜1.2 mg/L total rare earth elements and ˜409 mg/L total majormetals (Al, Fe, Si, Co, Mn, Ca, Mg, Ni, S) at pH 3.4 was transportedfrom the A-34 site. Table 19 provides data obtained from a detailedassay of raw water, i.e., untreated AMD. A portion of the 5,000 gallonraw water, i.e., a 1,000 gallon batch of untreated AMD, was adjusted topH 4.5 using a hydrated lime slurry utilizing the follow approach.Briefly, the raw water was placed in a 1,100-gallon tank (Clarifier #1)equipped with a Endress Hauser Liquiline CM 448 pH meter and a Sew-Eurodrive paddle mixer. While mixing occurred, the Liquiline pH metercommunicated with a Cole Parmer Master Flex L/S peristaltic pump to addlime slurry at a rate of 150 mL/min (26 g lime/liter of water) until thepH 4.5 was obtained. When pH 4.5 was obtained and stabilized, the mixingwas stopped and the solids were allowed to settle to the tank bottom bygravity for approximately 1 hour. The supernatant, referred to as the pH4.5 supernatant, comprised the liquid above the settled solids and wasdetermined to have a ˜82% reduction in aluminum (11.8 mg/L), a ˜98%reduction in iron (0.1 mg/L), and a ˜17% reduction in silica (14.6 mg/L)based on the amounts previously determined to be present in theuntreated water. It was further determined that approximately 99% of therare earth elements remained in the pH 4.5 supernatant. The solids(sludge) were removed from Clarifier #1 and were sent to a finaldisposal area.

TABLE 20 Levels of Various Metals in Untreated AMD. Elements UnitsUntreated AMD Al mg/L 64.3 Ca mg/L 197.0 Co mg/L 0.8 Fe mg/L 3.8 Mg mg/L93.3 Mn mg/L 24.2 Na mg/L 3.9 Ni mg/L 0.9 Si mg/L 17.6 Zn mg/L 2.6 TMMmg/L 408.5 Sc mg/L 0.0 Y mg/L 0.3 La mg/L 0.1 Ce mg/L 0.2 Pr mg/L 0.0 Ndmg/L 0.2 Sm mg/L 0.1 Eu mg/L 0.0 Gd mg/L 0.1 Tb mg/L 0.0 Dy mg/L 0.1 Homg/L 0.0 Er mg/L 0.0 Tm mg/L 0.0 Yb mg/L 0.0 Lu mg/L 0.0 TREE mg/L 1.2

The pH 4.5 supernatant was further processed to remove rare earthelements from solution. Briefly, the 4.5 pH supernatant was transferredto a rectangular shaped clarifier. This unit was scaled at a 1:10 ratioand constructed to model the design from the A-34 site clarifier design.This scaled clarifier comprises a rapid mix tank (4.5″×4.5″×12.5″)equipped with a Fisher Scientific jumbo stand mixer, a slow mix tank(24″×12″×11.5″) equipped with Caframo stand mixer and a clarifier tank(120″×17.75″×14.5″). The slow mix tank was equipped with a EndressHauser Liquiline CM 448 pH meter that communicated with a Cole ParmerMaster Flex US peristaltic pump. The pH 4.5 supernatant was pumped intothe clarifier continuously at rate of 1 gpm via a Cole Parmer MasterFlex UP peristaltic pump. The peristaltic pump in communication with theLiquiline pH meter pumped lime slurry (26 g lime/L of water) into therapid mix tank at a rate of approximately 15 mL/min to obtain andmaintain a pH 8.5, i.e., forming the pH 8.5 solution. A polymerflocculent, PE 6070 polymer (Phoenix Solutions, LLC), was added to therapid mix tank using a Cole Parmer Master Flex US peristaltic pump andwas added at a rate of 1 mL/min. The polymer flocculant solution wasprepared by adding 2 mL of neat PE 6070 to one liter of processed water,resulting in a 2 ppm polymer solution, that was used in an amount of0.25 mL PE 6070 solution per liter of pH 8.5 solution. The rapid mixedwater was flowed across a weir uniformly to the slow mix tank. Withoutwishing to be bound by a particular theory, it is believed that thelarger slow mix tank reduced the water velocity to allow the pH inducedparticles to agglomerate. Without wishing to be bound by a particulartheory, it is further believed that the internal baffle also added tothe agglomeration by forcing the floc particles to dive through theslurry solution to allow additional contact with the floc particles. Theagglomerated particles cross the weir uniformly to the clarifier. Thesolids settled in a parabolic curve to the bottom of the clarifier in 15minutes or less after exiting the slow mix tank. The settled supernatantwas decanted from the clarifier's exit port and discarded as treatedwater. The settled solids, i.e., the hydraulic pre-concentrate (HPC),were retained and removed via a port in the sump bottom of the clarifieralong with a portion of the supernatant in order to minimize solidsloss. Approximately 98% of the rare earth elements and the remainder ofthe total major metals were determined to be recovered to the solids.Approximately 83% of the calcium (247.9 mg/L), ˜63% of the magnesium(61.8 mg/L), ˜56% of the manganese (14.1 mg/L), and ˜39% of the Silica(5.7 mg/L) remained in the effluent water that reports to theclarifier's discharge point.

Example 8: Processing of Hydraulic Pre-Concentrate (HPC) to FormDewatered HPC

Forty gallons of saturated settled solids, i.e., hydraulicpre-concentrate (HPC) prepared as described above in Example 7, weretransferred to a 50-gallon Tamco 60° cone bottom tank (primary conetank) for dewatering. The HPC entered the cone tank was determined tohave a solids concentration of ˜0.2% solids. Following 1 hour ofsettling by gravity, the solids content reached ˜1% solids in thesettled material. Approximately 20 gallons of supernatant water wasdecanted through a port installed in the side of the cone tank as cleanwater and was discarded. Ten gallons of the 20 gallons of the settledsolids were transferred to a 10-gallon (secondary cone tank) AceRoto-Mold 60° cone bottom tank. This slurry settled for approximately 1hour. Following the solids settling, approximately 2 gallons ofsupernatant water was removed as clean water through a port installed inthe side of the tank. The resulting dewatered HPC, i.e., settled solidsslurry retained in the cone bottom tank had a solids content of ˜1.4%.

Example 9: PLS Preparation

Approximately 738 mL of the dewatered HPC comprising 1.4% solids HPCslurry, prepared as described above in Example 8, was transferred to a1000 mL glass beaker equipped with a Caframo stand mixer and MettlerToledo bench top pH meter. The dewatered HPC was acid leached with ACSgrade (93%) sulfuric acid. Approximately 8.2 mL of sulfuric acid wasadded dropwise with a plastic dropper until the pH stabilized at pH 3.0.Two mL of the 2 ppm PE 6070 polymer solution (prepared as describedabove) was added per liter of the sulfuric acid treated dewatered HPCwith mixing in order to flocculate the acid leached residual solids. Thesolution mixed for 5 minutes after the flocculent solution addition,then was allowed to settle for 20 minutes after mixing was stopped. TheREE enriched supernatant was removed via a pump and filtered through a1-micron pore size bag filter assembly to ensure no solids transferredto the next process step, i.e., a first filtered REE enrichedsupernatant. The flocculated acid leached residuals (PLS entrained tankbottoms) were then filtered through the 1-micron pore size bag filterassembly to capture additional liquid PLS, i.e., a second filtered REEenriched supernatant. The first filtered REE enriched supernatant andthe second filtered REE enriched supernatant to form the enriched PLSfiltrate. Analysis of the enriched PLS filtrate indicated a 93% recoveryof rare earth elements from the dewatered HPC material with a TREEconcentration of 83 mg/L. The full elemental composition of the enrichedPLS filtrate and recovery of elements from HPC to PLS can be found inTable 21 below.

TABLE 21 Recovery—HPC to PLS. % Recovery from HPC Elements Units pH 3.0PLS to PLS Al mg/L 1,050.5 78% Ca mg/L 449.5 96% Co mg/L 40.6 90% Femg/L 0.6  1% Mg mg/L 396.9 98% Mr mg/L 317.9 73% Na mg/L 5.0 N/A Ni mg/L30.2 76% Si mg/L 641.7 73% Zn mg/L 177.1 N/A TMM mg/L 3,069.5 79% Scmg/L 0.3 N/A Y mg/L 23.7 97% La mg/L 5.7 98% Ce mg/L 10.8 77% Pr mg/L2.9 96% Nd mg/L 15.4 97% Sm mg/L 4.6 96% Eu mg/L 1.1 96% Gd mg/L 6.7 96%Tb mg/L 1.0 97% Dy mg/L 5.1 96% Ho mg/L 1.0 96% Er mg/L 2.6 96% Tm mg/L0.3 96% Yb mg/L 1.7 95% Lu mg/L 0.2 96% TREE mg/L 83.0 93%

The enriched PLS filtrate (736 mL) was transferred to a second 1000 mLglass beaker containing a Caframo mixer and a Mettler Toledo bench toppH meter. Approximately 5 mL of 20% ammonium hydroxide was added to thebeaker to raise the pH to remove additional major metals. The ammoniumhydroxide was added dropwise with a plastic syringe to the PLS whilemixing until the pH reached pH 4.4 The resulting residual generatedthrough neutralization was flocculated by addition, with mixing, of twomL of the 2 ppm PE 6070 polymer solution (prepared as described above)per liter to ammonium hydroxide treated enriched PLS filtrate.

Following flocculent solution addition, mixing was stopped and thesolution was allowed to settle for 1 hour, then the supernatant wasremoved with a pump. The flocculated neutralization residuals werefiltered with a bag filtration unit through a 1-micron filter media toform the neutralized enriched PLS filtrate, which was transferred to aPLS storage tank. Analysis of the neutralized enriched PLS filtrateindicated that 89% of the aluminum and 82% of the silica was removedfrom the enriched PLS filtrate as precipitated solid. No measurable rareearths were lost due to the neutralization. The neutralized enriched PLSfiltrate can be further processed as needed. An elemental analysis ofthe neutralized enriched PLS filtrate can be found in Table 22 below.

TABLE 22 Levels of Metals in Neutralized PLS. Neutralized Elements UnitsPLS Al mg/L 115.6 Ca mg/L 494.5 Co mg/L 43.4 Fe mg/L 0.1 Mg mg/L 420.7Mn mg/L 324.3 Na mg/L 0.0 Ni mg/L 29.9 Si mg/L 115.5 Zn mg/L 159.3 TMMmg/L 1,703.2 Sc mg/L 0.0 Y mg/L 23.4 La mg/L 5.8 Ce mg/L 10.1 Pr mg/L2.9 Nd mg/L 16.0 Sm mg/L 4.2 Eu mg/L 1.0 Gd mg/L 6.3 Tb mg/L 0.8 Dy mg/L4.4 Ho mg/L 0.8 Er mg/L 2.2 Tm mg/L 0.2 Yb mg/L 1.2 Lu mg/L 0.1 TREEmg/L 82.6

Example 10: PLS Preparation—Variation of Acid

The method described above in Example 9 was followed in the studiesdescribed herein following, but with modification of the acid usedand/or pH endpoint that the acid was used to adjust to. Except as notedin the following, the method of Example 9 was followed in all respectsusing the same dewatered HPC comprising 1.4% solids HPC slurry, preparedas described above in Example 8.

Variation 1: The dewatered HPC was acid leached with 6M HCl instead ofACS grade (93%) sulfuric acid as described in Example 9. The 6M HCl wasadded until the pH stabilized at pH 3.0. Following this acid leachingstep, the rest of the method described in Example 9 was followed. UsingHCl as the leachate, it was determined that a 93% recovery of rare earthelements from the dewatered HPC material was obtained with a TREEconcentration of 87 mg/L at pH 3.0.

Variation 2: The dewatered HPC was acid leached with 68% nitric acidinstead of ACS grade (93%) sulfuric acid as described in Example 9. The68% nitric acid was added until the pH stabilized at pH 3.0. Followingthis acid leaching step, the rest of the method described in Example 9was followed. Using 68% nitric acid as the leachate, it was determinedthat a 93% recovery of rare earth elements from the dewatered HPCmaterial was obtained with a TREE concentration of 84 mg/L at pH 3.0.

Variation 3: The dewatered HPC was acid leached with ACS grade (93%)sulfuric acid as described in Example 9, but the sulfuric acid was addeduntil the pH stabilized at pH 3.5 instead of pH 3.0. Under theseconditions, it was determined that a 89% recovery of rare earth elementsfrom the dewatered HPC material was obtained with a TREE concentrationof 72 mg/L at pH 3.5. It should be noted that the sulfuric acid usagedecreased from 11.1 g/L to 7.4 g/L by leaching to pH 3.5 instead of pH3.0.

Example 11: PLS Preparation—Variation of Neutralization Conditions

The method described above in Example 9 was followed in the studiesdescribed herein following, but with modification of the base usedand/or pH endpoint that the base was used to adjust to in theneutralization step. Except as noted in the following, the method ofExample 9 was followed in all respects using a similar dewatered HPCthat was prepared as described above in Example 8.

Variation 1: In a variation from Example 9, instead of using 20%ammonium hydroxide to neutralize the solution, a 50% sodium hydroxidesolution was used as the neutralizing agent. Under these conditions, itwas determined that ˜88% of the aluminum and ˜69% of the silica wasprecipitated from acid solution. No measurable rare earths were lost tothe solid formed by neutralizing with sodium hydroxide at pH 4.4.

Variation 2: The procedure of Example 9 was followed using the sameneutralizing solution, i.e., 20% ammonium hydroxide, except that the pHwas adjusted to pH 4.0 instead of pH 4.4. Under these conditions, it wasdetermined that ˜53% of the aluminum and 49% of the silica wereprecipitated during the neutralization step. No measurable rare earthswere lost to the solid formed by neutralizing at pH 4.0.

Example 12: PLS Preparation—Reproducibility

The method described above in Example 9 was followed in the studiesdescribed herein following in all respects using the same dewatered HPCcomprising 1.4% solids HPC slurry, prepared as described above inExample 8. Each of the following represents an independent run of themethod to determine reproducibility of the disclosed method.

In a second trial of Example 9 that matched the original conditions andprocess from the test above results determined that with a 1.5% solidsdewatered HPC, acid leaching to pH 3 with sulfuric acid yielded a 95%rare earth element recovery with a TREE concentration of 106 mg/L.Furthermore, when the resulting PLS was neutralized with ammoniumhydroxide 97% of the aluminum and 75% of the silica was precipitated outof the solution. No measurable rare earth elements were lost to thesolid formed through neutralization.

In a third trial of Example 9 that matched the original conditions andprocess from the test above results determined that with a 1.4% solidsdewatered HPC, acid leaching to pH 3 with sulfuric acid yielded an 82%rare earth recovery with a TREE concentration of 105 mg/L Furthermore,when the resulting PLS was neutralized with ammonium hydroxide 85% ofthe aluminum and 89% of the silica was precipitated out of the solution.No measurable rare earth elements were lost to the solid formed throughneutralization.

The foregoing demonstrated the good reproducibility of REE recovery andTREE concentration.

It should be emphasized that the above-described embodiments of thepresent disclosure are merely possible examples of implementations setforth for a clear understanding of the principles of the disclosure.Many variations and modifications may be made to the above-describedembodiment(s) without departing substantially from the spirit andprinciples of the disclosure. All such modifications and variations areintended to be included herein within the scope of this disclosure andprotected by the following claims.

What is claimed is:
 1. A method for preparing a hydraulicpre-concentrate, the method comprising: (a) contacting a raw materialwith a first base in an amount sufficient to adjust the pH to a valuefrom about 4.0 to about 6.0, thereby forming a mixture comprising afirst aqueous phase and a first solid concentrate; (b) separating thefirst aqueous phase from the first solid concentrate, thereby forming aseparated first aqueous phase; (c) contacting the separated firstaqueous phase with a second base in an amount sufficient to adjust thepH to a value from about 7.0 to about 9.0, thereby forming a mixturecomprising a second aqueous phase and a hydraulic pre-concentrate; (d)removing the second aqueous phase and collecting the hydraulicpre-concentrate; wherein the raw material comprises rare earth elements;and wherein the hydraulic pre-concentrate is enriched in rare earthelements and critical minerals.
 2. The method of claim 1, wherein theraw material comprises acid mine drainage associated with a coal mine, ahard rock mine, or combinations thereof.
 3. The method of claim 2,wherein the hydraulic pre-concentrate is prepared at or proximal to thecoal mine, the hard rock mine, or combinations thereof.
 4. The method ofclaim 1, wherein the raw material comprises raw acid mine drainage(AMD), an AMD precipitate (AMDp), an enriched AMD precipitate (eAMDp),or combinations thereof.
 5. The method of claim 1, wherein the rawmaterial has a pH less than about 4.0.
 6. The method of claim 1, whereinthe first base comprises a base selected from ammonium hydroxide, sodiumhydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide,ammonium carbonate, sodium carbonate, potassium carbonate, calciumcarbonate, magnesium carbonate, and a combination thereof.
 7. The methodof claim 6, wherein the first base comprises calcium hydroxide.
 8. Themethod of claim 1, wherein the contacting the raw material with thefirst base is in an amount sufficient to adjust the pH to a value fromabout 4.0 to about 4.5.
 9. The method of claim 1, further comprisingoxidation; and wherein oxidation is mechanical oxidation,electrochemical oxidation, chemical oxidation, or combinations thereof.10. The method of claim 9, wherein oxidation comprises adding anoxidizing agent to the raw material and the first base.
 11. The methodof claim 10, wherein the oxidizing agent comprises a peroxide, ozone, apermanganate, or combinations thereof.
 12. The method of claim 1,wherein the second base comprises a base selected from ammoniumhydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide,magnesium hydroxide, ammonium carbonate, sodium carbonate, potassiumcarbonate, calcium carbonate, magnesium carbonate, and a combinationthereof.
 13. The method of claim 12, wherein the second base comprisescalcium hydroxide.
 14. The method of claim 1, wherein the contacting theseparated first aqueous phase with the second base is in an amountsufficient to adjust the pH to a value from about 8.0 to about 8.5. 15.The method of claim 1, wherein the removing the second aqueous phase andcollecting the hydraulic pre-concentrate carried out using a clarifier,a settlement basin, a flexible planar geotextile fabric of woven ornonwoven construction, or combinations thereof.
 16. The method of claim1, further comprising: (e) transferring the hydraulic pre-concentrate toa geosynthetic geobag; and (f) conditioning the hydraulicpre-concentrate in a first conditioning tank for a period of timesufficient and a temperature suitable for the solids concentration inthe geosynthetic geobag to increase from about 1.1-fold to about 15-foldcompared to the solids concentration of the hydraulic pre-concentrate.17. The method of claim 1, further comprising: (e) transferring thehydraulic pre-concentrate to a first conditioning tank; and (f)conditioning the hydraulic pre-concentrate in the first conditioningtank for a period of time sufficient and a temperature suitable for thesolids concentration in the lower sloped portion to increase from about1.1-fold to about 15-fold compared to the solids concentration of thehydraulic pre-concentrate; thereby forming in the lower portion of aconditioning tank a first conditioned hydraulic pre-concentrate.
 18. Themethod of claim 17, wherein the period of time sufficient and thetemperature suitable for the solids concentration in the lower slopedportion to reach a first conditioned pre-hydraulic solids concentration;wherein the first conditioned pre-hydraulic solids concentration isincreased from about 1.2-fold to about 10-fold compared to the solidsconcentration of the hydraulic pre-concentrate; wherein the period oftime is from about 10 min to about 72 hours; and wherein the temperatureis from about 5° C. to about 50° C.
 19. The method of claim 1, furthercomprising collecting the first conditioned hydraulic pre-concentrate;wherein the collecting further comprises: (g) transferring the firstcondition hydraulic pre-concentrate to a second conditioning tank; and(h) condition the first conditioned hydraulic pre-concentrate in thesecond conditioning tank for a period of time sufficient and at atemperature suitable for the solids concentration in the lower slopedportion to increase from about 1.1-fold to about 5-fold compared to thesolids concentration of the first conditioned hydraulic pre-concentrate;thereby forming in the lower portion of the second conditioning tank asecond conditioned hydraulic pre-concentrate.
 20. The method of claim19, wherein the period of time sufficient and the temperature suitablefor the solids concentration in the lower sloped portion to increasefrom about 1.2-fold to about 5-fold compared to the solids concentrationof the hydraulic pre-concentrate is a period of time from about 30 minto about 72 hours at a temperature from about 5° C. to about 50° C. 21.A method for preparing a pregnant leach solution, the method comprising:transferring the first conditioned hydraulic pre-concentrate of claim 17or the second conditioned hydraulic pre-concentrate of claim 19 to amixing tank; and adding a first acid to the mixing tank in an amountsufficient to adjust the pH from about 2.0 to about 4.0, thereby formingthe pregnant leach solution; wherein the first acid is mixed with thefirst conditioned hydraulic pre-concentrate or the second conditionedhydraulic pre-concentrate as the first acid is added.
 22. The method ofclaim 21, wherein the first acid is a mineral acid.
 23. The method ofclaim 22, wherein the mineral acid comprises a mineral acid selectedfrom nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid,sulfurous acid, and combinations thereof.
 24. The method of claim 21,further comprising adding a flocculating agent, coagulating agent, orcombinations thereof to: (a) the first conditioned hydraulicpre-concentrate; and/or (b) the second conditioned hydraulicpre-concentrate.
 25. The method of 21, further comprising neutralizingthe pregnant leach solution by contacting the pregnant leach solutionwith a third base in an amount sufficient to raise the pH of thepregnant leach solution to a pH of from about 4.5 to 5.0, therebyforming a neutralized pregnant leach solution.
 26. The method of claim1, further comprising adding a flocculating agent, coagulating agent, orcombinations thereof to: (a) the mixture comprising the first aqueousphase and the first solid concentrate; and/or (b) the mixture comprisingthe second aqueous phase and the hydraulic pre-concentrate.